I'm just going to assume that the +1 action line will be cut, because it's just extra complexity and power that doesn't add that much since you usually wouldn't want to trash an action anyway.
It's also worth mentioning that the top is already a stronger version of Remodel, thus worth $5+ even without the action. The reaction should probably be on the weaker side or account for it some other way. Having it react to treasure gaining may be enough, since it incentivizes using the card to gain a Treasure instead of an Action.
So, maybe something like this?
When any player gains a Treasure card, you may discard this from your hand. If you do, +2 cards.When a player gains a Treasure card, you may discard this. If you do, gain a copy of that Treasure card, putting it into your hand [or on your deck or somewhere else].
That can still cause the weird multiplayer gain chains. Suppose you gain a Harem. Now you have to slow down and go around in turn order to see if anybody will use their reaction. You may have to do it for every gain, even when nobody has the reaction in hand, because otherwise you'll give away information when you make a point of asking if anybody before you wants to react. And even after you've gone around the circle once, you may have to go around a second time since a player who passed on reacting to the original gain may want to react to your use of the reaction (likely involving emptying piles).
Having it gain a specific Treasure (Copper, Silver or Gold) would help. The pile is less likely to empty, so turn order won't be as much a concern.
But maybe it could do a similar thing without gaining?
When any player gains a Treasure card, you may discard this from your hand. If you do, reveal a Treasure card from your discard pile and put it [into your hand/on top of your deck].The nice thing is that it still has some symmetry with the top. I worry that this is getting too lengthy though.