I'm just curious if some of these areas have been explored, and what your thoughts might be:
Anti-Chancellor:
When you play this card, you may immediately shuffle your discard pile, and place it on top of your draw pile.
Card-Hunter: (Duration?)
When you play this, name a non-VP card. If the named card is played before the start of your following turn by any player, you may gain a copy of it.
City/Fairgrounds/Trade Route combination (Card "X" below):
Place a token on each of the starting kingdom cards. Anytime a card is gained for the first time, remove it's token and place it on a mat. Card "X" does A, B, or C depending on how many tokens are on the mat.
(The idea is to be a power-up card like city, that plays off Fairgrounds desire for unique cards, instead of piles drained. This is, I think, done best in a Trade Route fashion)
Anyway, just some thoughts on design space ideas that may not have much coverage yet.
Thoughts?