I've been mulling over another risky investment VP gainer, dependent on pile depletion. Two versions of it, both too wordy at the moment:
Version A--one card:
$2--Action/Hex
-1 VP
Count the number of empty supply piles. If there are...
none, +1 card, +1 action
exactly 1, you may trash this. If you do, gain a Duchy.
2 or more, you may trash this. If you do, gain a Province.
Version B--two cards:
Card X
$2--Action/Hex
-1 VP
+1 Card
+1 Action
Count the number of empty supply piles. If there are...
none, you may trash this and gain a Card Y
1 or more, you may trash this and gain a Duchy
Card Y
$3*--Action/Hex
-2 VP
+1 Card, +1 Action
If there are 2 or more supply piles empty, you may trash this and gain a Province.
In Version A, the pertinent risks are (1) the game ends on Provinces/Colonies before another pile is depleted and (2) deciding whether to cash out early for Duchies or try to hang on for Provinces. The card is not too detrimental, as a cantrip, so long as no piles have been depleted. After that, keeping them can past Duchy-ripeness can get in your way without good village support.
In version B, card X is a cantrip regardless of the number of empty supply piles. But once there is at least one empty pile, you are locked out of the trash-for-Province card, card Y. Being harder to get in the first place, I reverted this to a cantrip as well, but made the penalty for failure steeper by giving it -2 VP.
Other potential modifications:
Change the timing of the trash-for-VP to when you discard from play, allowing your buys to empty out a supply pile for you.
Change wording to "supply piles other than [this card's name]" to hinder a simple race to the bottom of this card's pile.