I think it would be cool if we had to talk to an NPC who gives you a random "crystallized item" that you have to use to accumulate attachment points for, and then that item becomes materia after you reach 100% with it. This said item can be random, like a weapon of any type, or some kind of armor.
At least that way we don't have to sacrifice our own (in some cases) hard to earn gear. I would feel better about loosing gear that I know would be lost for a good cause.