Hmm.. I would be nice to have some kind of wildcards craftable.
Lets say you can trade 5 cards into a token of the same rarity. These tokens can be exchanged into other cards of the same rarity. This would help the players getting hands on cards they really want for their decks, while shredding alot of others.
The obvious problem would be the price differences (who wouldn't like to buy 5x Curse Orb with ~40 bfp each in order to trade them for Enlightenment?). In order to prevent (or at least lessen) this issue, the cards could require a different amount of tokens, if you want to get