I think it would be interesting to have an ingame "Forge" of sorts (similar to WoE's talent "Crafting") where you can merge cards to create new ones. With the implication that more quests will be upon us and with so many potential new items coming out of WoE, it's possible there could be "item cards" won from quests that may or may not be useful in battle(sort of like extra cards that you could use, but they're inferior to metagame-focused cards, which are designed soley for the game), but when forged create more metagame-focused cards.
For example:
Completing a quest to help a farmer, I gain a Pitchfork. Pitchfork is a Weapon that deals 1 damage per turn. Not so great, right? However, if I forge a Pitchfork with a Water Crystal (which may or may not have an effect), I create a Trident/Poseidon. As you can see, this also makes rarer cards easier to obtain.
Forging costs 1,500 electrum, and I think adding a percent chance for it to fail would be a good idea too, if codable.