You could call this a fan set, as it's kind of designed to be such. The reality is it's an exploration into different mechanics. I made these cards through being an enthusiastic observer of the design of Dominion, not because I have a play group who wanted them. That said, most of the cards have been tested to some extent.
Revolution takes the actions one needs to play Action cards and makes them more like a currency. You can collect tokens to get +actions whenever you need them, and you can also be 'owing' an action, so you have flexible control of your Action phase. There are also Treasure focuses, and the mix of the two aims to make a set that gets players to adapt to each individual turn carefully, as they can be very different.
Mechanics: Action tokens, a -1 action State, a set of cycling start-of-turn effects.
There are also Duration cards, Night cards, and something like a Traveller.
TL;DRHere's the set so far in miniature. Click a card to enlarge it.
Kingdom cards:




























A shuffled pile of 12 landscape cards that give their effects immediately at the start of each player's next turn, then change for the next one the following turn. More rules later:











(A note on the use of internet images: the only intended purpose of these card mock-ups is to present the ideas on this forum thread in an easy to understand format. I do not intend to print them out or post them anywhere else online. If I later do, I will create my own artwork.)
Explaining the new mechanicsAction tokens - there are cards that let you collect Action tokens. They're just like coin tokens from Guilds, only when you spend one, you get +1 Action. You can do this in the same manner as Coin of the Realm, after playing an Action or before you play any during your Action phase. When you spend one, you can keep it in the play area after the Action you last played, for ease of tracking your action count, then put it back in the box at Clean-up.
The -1 action State, Exhausted
Exhausted - State
When you next have unused actions during your Action Phase, immediately return this and -1 Action.
There would be 6 of these IRL, 1 per player. Some cards in this set take Exhausted as a setback to being extra powerful, so the Action cards effectively use 2 actions. After taking Exhausted, whenever you next have actions left during your Action phase, this gets immediately returned and you have 1 less action. If you end your Action phase still having Exhausted, it will stay over to next turn, and be returned at the start to take away your starting action.
You'll notice all of the cards that take Exhausted check that you do take it. This is because of Thrones - you can't take more than 1 Exhausted to get the extra effects more than once.
Cycling start-of-turn effects, WeatherThey are a pile of 12 landscape cards which you shuffle before each game, and keep face down except the top one. Before each of his turns, the player going first discards the top Weather (just as you discard Boons), and each player gets the effect of the Weather immediately at the start of their next turn (they do not get it for extra turns through Outpost or its variants), before any other 'at the start of your turn' effects. The Weather for next turn is turned over at the same time, so players know what's coming. When the pile is empty, it is reshuffled into a new pile: the last card of the pile is set aside, then discarded when the new deck is made.
Including them in a game would follow the same rules as Shelters, Platinum and Colony; if the first card randomly selected is a Revolution, or the majority of them are Revolutions, include them. (Though of course they're fan cards, and you can use them anyhow.)
So here they are:

Sunny - +1 Card, +1 Action
An extra action for a bigger Action phase. +1 card to help more.
Stormy - take Exhausted
The opposite, -1 action. But if you're already Exhausted from last turn you get nothing.
Cloudy - +2 Cards, put 2 cards from your hand onto your deck
Card movement will always have an effect on your turn. This gets you to plan a bit.
Windy - discard 2 cards, +2 Cards
A Cellar fixed at 2 cards. Could be good, could be bad.
Rainy - if you have 4 or more cards in your hand, take one and put it anywhere in your deck
1 less card in your hand by Secret-Passaging something.
Showery - +1 Buy, + $1
Buying vanilla.
Snowy - this turn, cards (everywhere) cost $1 more
And the opposite, sort of.
Dry - this turn, cards are gained onto your deck
Mostly good, but bad for Victories.
Foggy - +1 Card, take Diverted, put a card from your hand onto Diverted
Diverted comes up later as well. Basically, whatever non-Victory you buy for the rest of this shuffle will miss the next shuffle, and the card you put on Diverted from hand will miss the next shuffle as well. It's a negative.
Mild - no effect
And two blank cards to make things, well, milder.
Changing - set this and the next two Weathers aside, then discard them. For this turn, each player gets both Weathers in the order they were set aside in
This one basically makes two Weathers appear at once, to make things a bit more different each game. You don't know what's coming, though. There are 12 cards, but with this the pile will run through on average 10 turns.
Example:
Alice starts her turn with a hand of Village, Colliery, 2 Estates and a Copper. She plays Village, drawing a Copper. Then she plays Colliery, getting + $2 and discarding an Estate. She chooses to take Exhausted; because she currently has 1 action left, Exhausted is immediately returned and she now has no actions left. Continuing the instructions, she discards the other Estate and gets a total $4. Entering her Buy phase, she has $6 to spend.
Bob has a hand of Colliery, Smithy, 2 Estates a Copper. He hasn't used the action token he got from when he bought the Colliery. Like Alice, he plays the Colliery, taking Exhausted and discarding both Estates for $4. He had no actions left when he took Exhausted, so it stays. He next chooses to spend his action token for +1 action, placing it to the right of his Colliery. But he can't play his Smithy; Exhausted takes priority and is returned, leaving him again with 0 actions. He really should have played them the other way round... If he did, he would have Exhausted carry over to the start of next turn, which would hurt or not depending on whether he draws any Actions.
INDIVIDUAL ANALYSISI explain each card, then give my thoughts on positives (
+) and negatives (
-) in its design.

Advancing Village - Action Reaction, $3 cost.
+1 Card
Take an Action token.
-
When this enters your hand outside of your Action Phase, you may play it immediately. (Discard it at your next Clean-up.)
Basically, this becomes a Village it enters hand outside of your Action phase (so including methods that aren't drawing too. There are plenty of ways to do this in the set, including of course the most likely case of drawing it at Clean-up), as you will start your next turn with the starting action and an action token. But even better than a Caravan Guard variant giving +1 action at the start of your next turn, you can use the action token on a later turn if you wish. Played in your Action phase, it has the lesser ability to convert a spare action into a token, or be a plain cantrip.
+: I feel it achieves difference with a Village card, in that, for one thing, it's good to open with it.
-: It's not a direct variant on any other card, so rules complications could deter people, such as interaction with Teacher tokens. Whatever the rules are for Caravan Guard should also apply to this.

Barometer - Action Duration, $4 cost.
Now and at the start of your next turn: name a type (Action, Attack, etc). Reveal the top 5 cards of your deck. Put the cards with the named type back in any order and discard the rest.
This one is yet to be tested. A sifter that lets you adapt your next draw to what you need now. And what you choose next turn won't always be the same as what you choose this turn.
+: It seems highly diverse in its utility yet not so much that it's useful in every kingdom. It would enhance this set very nicely if testing shows no problems.
-: Having 2 sort effects to do, and 2 decisions to call, it may be slow to play. It could also suffer from the same weakness as Navigator in being non-terminal. Hopefully the next turn effect balances this out.

Canal - Action, $6 cost.
+1 Buy
This turn, cards you haven't yet gained a copy of cost $2 less, but not less than $0.
Bridge variant. All Supply piles cost less until something is gained from them, no matter when and how many Canals you play or Throne during your turn.
+: Simple to read. That some piles can have their costs reduced and others not opens up a few new tricks.
-: A cost reduction of $2 is very powerful. It may be that this is dominant in too many kingdoms.

Colliery - Action, $3 cost.
+ $2
Discard a card.
You may take Exhausted. If you do, discard a card and + $2.
-
When you gain this, take an Action token.
Modest discard for benefit. Terminally discarding a card for $2 is very weak, but Colliery can do this twice, and the second time is stronger than the first (1 less handsize rather than 2). The discarding is not necessary for getting the $2, so you can get it with an empty hand. Colliery also comes with an action token, which can help its first play or be used for something else, something you don't mind paying $3 for.
+: It fills distinct niches rather than be good all the time, so isn't an automatic buy.
-: It could be too automatic as an opener, even if it is less useful later.
Components - Action, $3 cost
+1 Action
Return this and another Components from your hand to the Supply. If you return two Components, gain a Prototype from its pile.
-
When you gain this, gain a Silver onto your deck.
The first stage of a 'Traveller' that's hard to upgrade. It needs two copies to connect like Treasure Map, which would seem doable at $3 cost if not for the mixed bonus and hindrance of a top-decked Silver thickening the deck. If it should be that you don't connect them in good time, they can easily be returned so you can take your deck in a different direction. Or maybe you want the Silver and don't mind the extra card in your next shuffle.
+: I feel compelled by a Treasure Map that rewards you with a central engine piece.
-: The top-decked Silver could be too generous for $3 seeing what Components can later become. Or it could make them too situationally viable or swingy.
(I explain the upgrades after the kingdom cards.)

Diary - Treasure, $5 cost.
$2
When you play this, you may put a card from your hand onto your deck. If you do, take an Action token.
Two things you can find useful to do in your Buy phase, thinking about your next turn.
+: To quote what others have said, elegant.
-: Very good very often, it may be too cheap. At least it isn't much good in decks that draw themselves.

Diversion - Action Attack, $5 cost.
+ $2
Each other player takes Diverted. Those who already have it put a non-Victory from their hand costing from $3 - $6 onto their Diverted (or reveal they can't). Those who do draw a card.
Diverted - State
Non-Victory cards you buy are gained onto this. After you shuffle your deck, if there are any cards on this, discard them and return this.
This is a newer one, not tested in this form but I've arrived at it through testing. I was trying to make a different Attack, and since Exhausted is in the set I thought I could use a State. One that hits the Buy phase whilst the other Attack, Revolters, hits the Action phase. Delayed buys, a concept considered often on this forum, is what I first came to (although with the wording 'gained onto this' you can bypass it if you can get other gain locations specified, so you get the choice where a card goes). Non-Victories they buy miss the next shuffle. Additional plays make it a pseudo-Knight that delays cards from other players' decks.
+: I feel it would achieve difference if it's successful.
-: the Knight-like part could easily prove to be broken; actually, a fix comes to mind, which I'll get to later.

Entrepreneur - Action Reaction, $2 cost.
+1 Action
+ $1
If the Entrepreneur Supply pile is empty, +1 Card and +1 Buy.
-
When any other player trashes a card, you may return this to the Supply to gain a card costing up to $5.
A card that captures risky investment and opportunity, and adds potential mind games. It's a mere Copper to start with, but it can become a $5 cost card when its pile is empty (Market) or if an opponent trashes something. If it reacts to trashing, other Entrepreneurs are hindered in getting to their Market level.
+: The main thing I wanted to try and do was a card that reacts to trashing, as a means of 'nerfing' how good trashing is. It does achieve this, but it's better for adding player interaction.
-: for a card that benefits from other sources of +buy, it's a bit strange that it can later give lots of buys itself.

Foreign Art - Treasure, $5 cost.
$4
+1 Buy
When you play this, take Diverted and put this on it.
A big spike of money that delays what you buy from entering the deck (except Victories). It gets delayed as well.
+: Simple and effective.
-: Taking Diverted like this detracts from the card Diversion.

Furnace - Action, $4 cost.
+1 Buy
You may trash a card from your hand for + $2. If it wasn't a Treasure, trash up to 2 more cards from your hand.
-
When you buy this, you may take Exhausted. If you do, play this.
Principally a trasher that targets non-Copper junk. It can be payload with its +buy, but you need to trash a card in order to get the $2. But, when you buy the card, you can play it instantly for those times when your hand is set up just right to trash lots of stuff, and also buy something else with $2 less to spend. Yes, you're playing an Action in your Buy phase, but it's all safe as far as I can see. All of this immediate power in exchange for your next turn's starting action, because trashing is that good.
+: I feel it's a compellingly different trasher.
-: It's not a simple card to read and understand.

Innovator - Action, $5 cost.
Choose one: discard any number of cards, + $1 per card discarded; or draw up to 6 cards in hand.
You may take Exhausted. If you do, get the other choice.
Not yet tested. Handsize changing payload. Choose to discard for benefit, draw to 6, or take Exhausted for both either way round.
+: The format of choose one or Exhaust for both gives effective, balanced flexibility.
-: Could be too weak, it's only significantly good when Exhausted is taken.

Night Shift - Night Duration, $5 cost.
Take Exhausted. If you do, and the previous turn wasn't yours, take another turn after this one.
An Outpost variant that starts your bonus turn without the initial action. You could 'unlock' your Action Phase with Duration Villages or an action token, or simply skip it.
+: Simple, elegant, and a nice card to build around.
-: There are enough ways around the setback that this could be too strong.

Parade - Victory, $5 cost.
Worth 8VP - VP equal to the difference in the number of Actions and Treasures in your deck.
-
When you gain this, if you have a different number of Actions and Treasures in play, trash it.
Alt VP aiming to reward players who build their deck in a defined way. It's hard to actually gain, but when you do it should be worth it.
+: If it's successful, it will add a compelling way to win the game.
-: It may be so hard to get that it's irrelevant in most games. Or it makes for a strategy too heavily dependent on chance. I can't be confident in whether the maximum VP is balanced.

Potteries - Action, $5 cost.
Trash a card from your hand.
You may take Exhausted. If you do, gain a card costing up to $5 more than the trashed card, putting it into your hand if it costs up to $2 more.
Remodel variant going big if you take Exhausted. You can gain a cheaper card straight to your hand, or a much more expensive one.
+: It's strong payload, a good reason to build a deck to use 2 actions on it.
-: A Remodel going this big a cost increase could be uninteresting, particularly when compared to Altar.

Purist - Action Treasure, $4 cost.
If it's your Action phase, +3 Actions.
If it's your Buy phase, this is worth $1, and if you haven't played any non-Treasures this turn, +1 Card.
A newer one. A card that either supports a (mostly) pure Action phase turn or a pure Buy phase turn. Wanderers are card-shaped things you can play that aren't Treasures, so they would stop the Buy phase bonus as well as Actions.
+: It's simple to understand but not always simple to use.
-: Having said it's not simple to use, that could mean it's too weak. Or it could be uninteresting.

Revolters - Action Attack Duration, $4 cost.
Until your next turn, when another player starts their Buy phase with no unused actions, they gain a Curse.
At the start of your next turn, take an Action token.
A -1 action Attack. If it handed out Exhausted, it could pin everyone else out of every Action phase, which would be too strong. So it implies -1 action by giving the opponents the choice between it or a Curse. And so it becomes this set's Curser.
+: It's a different way to attack. It gives more reasons for Action tokens over +Actions.
-: Generally, Attacks are payload cards, and their self bonus reflects this. An Action token is a bit strange here, even though it is the opposite of what the Attack does.

Steelworks - Action Night, $4 cost.
If it's your Action phase, gain a card costing up to $4, or if you have used 3 or more actions this turn it may cost $5.
At Night, you may trash this, to take an action token for every card you've gained this turn.
Untested in this form. Put simply, a Workshop variant that can let each gain for the turn come with an action token. If you play it as an Action, what it gains depends on the number of actions you've
used since playing it, so like Conspirator for played Action cards but instead actions. Returning Exhausted does count as a used action, as do played Wanderers.
Being the Night type, you can play this at the Night phase. But no matter which phase you play this in, 'at Night' (rather than 'otherwise' like that card called Werewolf) means you can trash it to take action tokens regardless. You'll get one more token if you play it as an Action, but you need to have the action to play it.
+: The cost upgrade I find a compelling goal to reach with this set. I wanted to fit taking tokens for gained cards somewhere in the set and it fits nicely here.
-: It feels like it falls between the price brackets of $4 and $5, so costing it $4 could be too cheap. Two new mechanics in one card makes it both extra unfriendly to new players and vulnerable to future cards (unless I miss something about the present ones?).

Taskmaster - Action, $4 cost.
+1 Card
+1 Action
When you play an Action from your hand, you may first turn an unturned Taskmaster you have in play sideways and take Exhausted. If you do both, play the Action twice.
As Royal Carriage is a Throne that looks 'backward' to any Action played, this Throne looks 'forward' to anytime later in the turn. You turn the card on its side when you Throne something, to indicate that it's been used. If you Throne a Duration, the sideways Taskmaster stays in play with it. This is also a cantrip, which is counterbalanced by taking Exhausted. If you Throne a Taskmaster, you will get 2 cards 2 actions (-1 action if you Taskmaster itself, so a chain of them will all be Labs except for the first one), but it won't change how many times it can Throne things; it can still only be turned once.
+: It applies Exhausted boosts to every Action in the game, to make more different ways to play an engine.
-: Nothing else turns cards in play like this, so could come against future rules issues. It can't turn itself face down like that card called Necromancer does, as face down cards in the play area aren't 'in play'. And for all this complication, is it different enough from Royal Carriage?

Textile Mill - Action, $5+ cost.
+3 Cards
You may take Exhausted. If you do, +2 Cards.
-
When you buy this, you may overpay for it. Take an action token per $1 overpaid.
Smithy that you can double (another +2 handsize) by taking Exhausted. Because this is short text, it has overpay for Action tokens added on, which for one thing can let it be a draw card for Big Money decks with the advantage of different price points.
+: Simple yet effective.
-: Perhaps too strong. An overpay effect on a $5 may not see much use.

Tutor - Action Duration, $3 cost.
+1 Card
+1 Action
You may set aside a card from your hand. At the start of your next turn, if the card is an...
Action, play it;
Treasure, trash it;
neither type, discard it and +1 Card.
Duration that sets aside a card, then to do something with it that benefits the typical engine. Useful, but slow. For Crown (and Purist) you follow the instructions in order, play then trash them.
+: Simple and diverse in its use.
-: It could be too strong, or relevant too often, being both an early trasher and late cycler.

Wastelands - Victory, $5 cost.
Worth 5VP if you have 10 or fewer non-Victory cards in your deck, otherwise 2VP.
-
When you gain this, trash up to 3 cards you have in play.
Alt VP that rewards you for working with few payload cards, which you can do well in this set. Careful timing is needed to play it well. Or it can be a way you trash down to make an engine.
+: I feel it makes for a compelling different way to play the game.
-: 10 non-Victories could be too generous, or trashing 3 cards too generous. It's questionable if both this and Parade should be in the same set.
Components upgradesThere are 5 copies of each.

Prototype - Action Machine, $0* cost.
Take two action tokens. You may trash a Treasure from your hand, to gain a Treasure to your hand costing up to $3 more. Exchange this for a Machine.
(This is not in the Supply.)
The first of only 2 upgrade stages, as Components are a fair bit harder to upgrade than Page or Peasant. On play, you get two Action tokens and Mine, then you can upgrade it into a Machine, a type shared by the 3 different final stages. Each of these takes a powerful step in different directions. Prototype also is a Machine; this means you can, instead of upgrade it, choose to essentially discard it for a chance to draw and play it again on the same turn, and there's nothing to track if you do.
+: I believe it achieves self-discard without any problems. It makes for a smooth transition between Components (it can Mine the Silvers) and the final upgrades.
-: You can play Components and the Prototype on the same turn, which adds potential swinginess. The self-discard being on the middle upgrade rather than a final one could make some players sad to have to lose the ability.

Spinning Mule - Treasure Machine, $0* cost.
$1
While this is in play, after you play a Treasure (including this), +1 card.
(This is not in the Supply.)
If your deck is taking more of a money direction, you can take this upgrade to improve your Treasures immensely. After you play a Treasure, so after you resolve all a Treasure's effects (which are 'when' you play it), you draw a card. It looks strong, but it's delayed, and it's one card in a likely big deck. It needs to not have a buy on it to balance it further.
+: Simple, suitably powerful, a nice contrast to Steam Engine.
-: Very daring; it can so easily become broken in the future, and it arguably changes the whole game of Dominion to let Treasures draw the deck.

Steam Engine - Action Machine, $0* cost.
Discard up to 3 cards. Take an Action token per card discarded.
While this is in play, after an action token you spend gives +1 Action, you may use that action to play an Action card from your hand twice.
(This is not in the Supply.)
An upgrade for Actions as opposed to Spinning Mule for Treasures. Massively improve playing Actions by turning your Action tokens into Throne tokens while this is in play, but Exhausted still takes priority if it's there when a token is spent. You can put the token on the card when you Throne it, and if it's a Duration it can stay on over the other turns. If you use Taskmaster on a Steam powered card, it is played four times (you play it twice twice).
+: Tokens are a clean way to make a multi Throne Room. Both this and Spinning Mule are similar in being single power cards that need to be in hand each run through the deck.
-: Taskmaster and this are very similar. And the rule for both interacting on the same card may be technically questionable.

Patent - Action Machine, $0* cost.
Choose one: +2 Cards, +2 Actions or + $2, then this becomes the card on your Patent mat until it leaves play.
-
When you get your first Patent, move an Action card from the Supply that isn't on any other Patent mat onto your Patent mat.
(This is not in the Supply.)
Make your own power Action card, and prevent anyone else copying you. You get a copy of an Action in the Supply and add a vanilla bonus to it. The Patent mat could be like a mat from Seaside. If a game turns out to be a race for the best Patent, the players who lose can likely do well with a Steam Engine.
+: The added sense of uniqueness can feel nice to some, and it's a different way to get ahead in a game.
-: It's wordy. It's hard to tell if it's balanced.
And that's everything. I hope you found this an interesting read, whether you're an observer into Dominion design, or you're looking for inspiration for your own fan cards, or any other reason. Feel free to leave comments; I don't mind criticism, as it's essential to perfecting any design.
And thank you for reading.