Are you guys allergic to costs? This check is not complicated, does not create any rules ambiguity, improves the play patterns of the card, and makes play of the card simpler since it reduces decision making for the player of it as the player to his left has to only make one decision instead of X decisions (and is making decisions with full information which makes the choice easier). Allowing the Architect player to reveal X cards from hand makes Architect significantly stronger because with a little bit of hand-size increasing one can basically choose which card he trashes which is not the point of Architect. Architect is played because you want to Remodel something, anything, and it hardly matters what.
Well, it's new tech, so we are naturally weary. If it's not strictly necessary to get the card to do what you want, I would do without it. What would you say is the point of preventing 5$ cards from being remodeled?
In an earlier version, Architect was a cantrip with its
Advisor\
Remodel effect (it also did not have the "in games using this" which was added to make its play patterns more varied). Obviously the card was a bit frustrating when you draw something you don't want to trash, but it was actually fairly strong and very fast, so we removed the +1 Card.
Regardless, the problem came that it was almost always the right move to trash the other player's $5 cards. Those $5 cards do not often have good targets into which they can be remodeled-- while Architects can be speedy, they are not fast enough to get around players buying cards. If their $5 cards can be trashed and have no good targets as is normal, Architects become significantly weaker with each $5 card added to a player's deck. So the card rotted in uselessness.
This prohibition of targeting $5 cards allows the card to function as $5 cards are added to players' decks and maintains the speed in decision making of the card because the player to the left decides what is trashed with full information and the player of it only has to decide what he gains from there. Revealing 3 cards would require that the player of it decide which 3 cards he will reveal, then the left player has to play a dangerous guessing game because of the limited information presented to him, and then the player of it decides which card he gains.
5 words is quite a bit. It removes one "if", which makes the card easier to parse. It's not a huge deal, but it's there.
Technically, it removes a "may," not an "if." That "if" is stuck there. I can shorten it to "If there are no Treasures in your hand, you may reveal it and gain a Gold" which is the same number of words but a few characters shorter. It does have fewer clauses which might make it easier to parse.
Making the reveal mandatory means: the reveal is not an effect you are allowed to forget about (in a Treasure centric Kingdom, you can read Prospector once and then discard the "you may reveal your hand" bit); it makes the card less compatible with
Contraband (or any other cards that encourage deck tracking other players); and it might force players to gain Gold when they don't want to (which is not really a problem and I'd tell players to deal with it if it weren't for the previous two points).
Gaining a 4$ card to hand is crazy strong. Making all other players gain a 4$ card to hand for free is a crazy strong penalty. Sure, maybe they won't want to, but it's still crazy. The card would have to be playtested a lot to see if it works or not. Maybe people will simply avoid buying Gold or Prospectors in games using the latter, whether that happens to be the right decision or not? It's sort of a game of chicken here. Hard to predict.
It's really just cute. In many cases you are adding +$1 to another player's turn as well as another terminal Action to their deck. Sometimes it lets players get +$2, but that might just lead them to buy a Gold which will return the favor of gaining a Prospector yourself.
Prospector is a tempo trasher, and players rarely turn down the first one made available to them in this way, but you can only get so far with tempo trashers. Prospector has not proven strong enough to disallow buying Gold. In most cases players are gaining an additional +$1 to their turn by tossing out a Copper. Sometimes players will gain a Prospector because they have nothing left to trash but the other Prospector that is already in their hand.
Prospector is a fairly common opening in my numerous tests of it in spite of players' ability to pick it up later when another player gains a Gold because early trashing is very valuable. If a player decided to skip a needed Prospector on the belief that another player would drop one onto him, it might behoove another player to not buy a Gold as early because of it, but that scenario has never occurred.
I guess my concern with things is more logistical than anything else, and you can probably speak best to this having playtested these cards quite a bit: How do you find it is to manage all of the "In games using this" effects? A couple of people earlier posted suggestions about tokens or a new card color. I suppose that could be helpful but even so, with just nine of the cards you've revealed so far, if I'm playing with all of them in the same Kingdom I have to remember:
Your assumption of the effects becoming second nature is accurate, but more than anything else the effects are easy to remember because of how drastically they change the strategy of the board and are thus so constantly considered. When you start out plotting out how to get to $9 per turn (Countess) or you ask every turn if you want to use your extra Buy (Street) or trash Coppers from your hand (Slave Trade), the effects get engrained quickly. Inquisitor is the trickiest one to remember because its effect only applies once players are gaining Victory cards, and to that end I recommend placing the Inquisitor randomizer onto the Province pile to remind players of its effect.