A token system wouldn’t be a bad idea, but I would recommend making all of the drops have a lower drop chance, then every time someone reaches level 5 they get a token. Just talk to the grinding guy and have a menu pop up (similar to the menu of the goblin) where you can use your tokens to purchase the items. It would be nice if the prices were a little high also. Like 10 tokens for everything but the mount, and the mount being 25 or something of that nature.
EDIT: I actually thing this is an amazing idea after reading it back to myself. Please add this. It would give people something to work towards, and the drive to achieve transmogs. #KeepTheGrindAlive