Tinker
Types: Night
Cost: $5
Exchange a card from your hand for a card from the Supply costing up to $2 more than it.
Heirloom: Tin SnipsTin Snips
Types: Treasure, Reaction, Heirloom
Cost: $3
$1
When you return a card to the Supply, you may discard this from your hand for +3 Coffers.
I do agree that Tinker needs to cost $5 (which you changed in the image but not the text): Remodel is very nearly too strong for $4, let alone Remodel-with-a-benefit (and being non-terminal is a huge benefit, even if it has to trigger during the Night phase).
Tin Snips is this huge source of +Coffers, but has so little to play with it except Tinker. +3 Coffers is way too big for how frustrating it will be to align in the early game. I'd much rather Tin Snips trigger off trashing for it to play nicer with more Kingdom cards. Then it can give a more reasonable number of Coffers, and Tinker could trash instead of Exchange.
I mean if I did that I'd basically be making cards that already exist. The exchange-instead-of-trashing is The Whole Point of the card.
I did change Tin Snips to +2 Coffers tho, because +3 is too much - you hit that and a Swashbuckler? You've got your treasure chest in one go. Too much. But in the interest of having a game where you ignore Tinker and still use Tin Snips, I changed it to be a Silver instead of a Copper (and bumped the price up by one so we don't have to have Yet Another "Strictly Better" thread derailment on this board).
There isn't currently a non-terminal
Remodel, nor a
Remodel that ties into an Heirloom. Exchanging is a fine idea for a
Remodel variant, but it is not as though exchanging is the only unique part of Tinker. It seems to just make Tin Snips virtually only proc on Tinker instead of having a host of triggers. That reads odd to me, because I would think that Heirlooms should be designed to interact meaningfully with their Kingdom cards without being strictly defined by it.
Reducing Coffers to +2 is a major improvement to Tin Snips, especially with it giving +$2 on play: It massively reduces the frustration of missing as it goes from better $2 to worse $2. I'm not sure I like the effect it has on the opening, as $5/$3 is probably pretty silly on most boards compared to $4/$4.
Gild
Types: Action
Cost: $5
Trash a card from your hand. Gain a Gold.
Heirloom: IngotIngot
Types: Treasure, Heirloom
Cost: $3
$1. When you play this, if you have a Gold, Silver and Copper in play, you may trash this, to move your +$1 token to an Action Supply pile. (When you play a card from that pile, you first get +$1.)
I like Ingot a lot. I mostly worry that Gild will speed the game up too often that the +$1 token won't matter. I might take notes from
Altar and make Gild cost $6. It would be a weaker $6 for sure, but I worry it would be domineering as a $5 in how it doesn't increase your stop-density. Comparisons to
Mine are not warranted as this turns Coppers and even Estates into Gold, which is wildly better. Comparisons to
Dismantle might make more sense, but not quite because
Dismantle actually floods your deck when you're trashing Estates, so this remains wildly better than that official card too. I think it is unique enough, but plays largely against Ingot. I'm not sure how I'd feel better about it without complicating Gild's pure simplicity.
Foundation
Types: Action, Duration
Cost: $7
At the start of each of your turns for the rest of the game: you may trash a card from your hand, to gain a card to your hand costing exactly $1 more than it.
Heirloom: SafeSafe
Types: Treasure, Heirloom
Cost: $1
+1 Coffers. When you play this, you may put a card from your hand onto your deck.
I think Foundation should cost $8 mostly because being able to trash Golds for Foundations is probably too good in 2-player when you can also trash Foundations for Provinces. Even without that ability, having multiple Foundations would give you a lot of pile control, which is why I would go up to $8 instead of down to $6.
Fur Trader
Types: Action, Reaction
Cost: $4
Gain a Silver ot your hand. Put a card from your hand onto your deck.
When you would gain a card, you may reveal this from your hand. Discard any number of cards to instead gain a card costing up to $1 more per card discarded.
Heirloom: PeltPelt
Types: Treasure, Heirloom
Cost: $2
$1. You may trash a Silver from your hand to gain a card costing up to $4.
This version of your submission is much better overall. You are probably underselling Fur Trader's ability to discard your hand for a $5 gain early in the game. Most Kingdoms I buy Fur Trader would probably be for that Reaction. The key interaction between the two is probably using Pelt to trash a Silver and Fur trader to gain a $5 (functionally out of $4 in the form of Silver being trashed and a Fur Trader being discarded). It still costs a Buy most of the time, so I wouldn't call it overpowered. Fur Trader -> Workshop+ around draw is a fine idea, but playing Fur Trader is probably really bad.
I recommend a slight buff by having Fur Trader "gain a card costing exactly $1 more per card discarded" so you can typically block Curses by discarding 1 card. I might make Fur Trader gain 2 Silvers with no hand shenanigans so you can more easily align Pelt.