Ripping out a suggestion from another thread, it would be awesome if you could trade two items of a certain rarity that you didn't want for another random item of the same rarity. NB: I am NOT suggestion an ability to create entirely new card sets based on the cards associated with the items you sacrifice, because that would probably break the game. It's just a 2:1 trade-in scheme so you can liquidate the "useless" items you acquire, especially epics and legendaries, in a more useful manner than waiting for Randimar to finally turn up something worthwhile.
There are already several threads regarding crafting - and it's pro's and cons. This is the most recent one, and I'm sure you can dig some more up with a search: http://forums.cardhunter.com/threads/suggestion-crafting.3986/#post-39460
