Just had an idea for a card...
Swamp
$2 - Victory
Worth 6 VP
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When you gain this, if you have taken more than 2 turns (including this turn), trash this.
Basically, it's a victory card that is worth more points than it should be, but with the huge drawback that you can only get it as part of your opening. Costs $2 so that anyone could open Swamp/Swamp if they wanted to. Named Swamp because it's a land that slows you down.
Not sure at all about the VP... 6 sounds possibly too strong, like opening double-Swamp will too often be good. 4 sounds almost definitely too weak. While 5 just seems like a weird VP value for a card to have, I dunno.
It might be too simple of a decision; Big Money = get Swamp, Engine = avoid Swamp. Weak Engine = 1 Swamp but not 2. Maybe. I mean, if you open double-Swamp, and your opponent doesn't, then you only need 3 Provinces to his 5 to tie.
5 VP doesn't seem like a weird value to me.
I don't think Big Money is necessarily going to mean you want Swamp. It still slows you down a lot. More like, if you have good sifting or if your opponents are playing Militias, you want Swamp.
For the bottom, how about: After each player's second turn, remove all remaining Swamps from the Supply. (This does not count as an empty Supply pile.)
I guess the thing with 5 is just that no official cards are worth 5; though there are a few that can be. With 4; at least that's the most common worth of Fairgrounds.
The reason I thought big money vs engine is that I think of big money as commonly ending in closer scores than engines. Big money often ends by less than 12 points. But maybe I'm wrong in thinking that the same isn't true for engines.
As for the bottom; your wording is probably easier to play, but I liked the idea that the cards could still have some interaction in rest of the game. In the endgame it's a third pile you can empty; and it also combos well with Goons and Merchant Guild.
Finally; I just realized that this card helps the second player a bit... the second player can always choose to go the same route as player 1, but player 1 needs to decide on Swamp before knowing what his opponent is thinking. (Obviously this is true of all cards, but with Swamp it probably matters more).