The main idea is having sets of vouchers that disable some other from appearing. Here is some of my ideas
Empty Shelf: -1 pack in shop, shop only have mega packs
Empty Store: -1 card slot available in shop, reroll always cost $2.
Incompatible with Overstock and Reroll Surplus
Negative thoughts:
Foil, Holographic and Polychrome appear 2x less often
Negative appear 2x more often
Depressive mind: Foil, Holographic and Polychrome appear 4x less often
Wheel of Fortune can now apply Negative
Incompatible with Hone
Spectral merchant: spectral cards may appear in shop
Spectral Tycoon: spectral cards appear 2x more frequently
Incompatible with Tarot Merchant and Planet Merchant
Ghost deck now start with Spectral merchant
Future Device: +1 Ante, +1 hand, +$25
Time Machine: +1 Ante, +1 discard, +$25
Incompatible with Hieroglyph
If Ante 8 is skipped, Ante 9 are new goal
Loan: you can go up to -$15 in debt. At the start of Blind, set your $ to 0. You no longer get interest.
Bankrupt: you can now go up to -30$ in debt.
This effect is addictive to Credit Card (so, with Bankrupt and Credit card, you can have up to -$50)
Incompatible with Seed Money