It kind of gets annoying when I have to go through all the cards of a certain game, so wouldn't it be a great idea to have a blank trading card as a trading item (somewhat like the blank TF2 offers with the bag stuffed of items)?
I can't really think of any cons, but enlighten me if there are any.

EDIT: Or maybe a community thing where we use the booster pack items in the stead of game cards (referring back to the TF2 offers item; how we recognize unusual-typed TF2 offers as unusual offers).