If we opened the door on gear I'd want to somehow use WoW's transmog system instead of our current glamour system where you learn an item's appearance.

We can still use glamour prisms to "learn" the appearance (and bind the item in doing so) and maybe also to apply the appearance. Plates could still be used to save outfits. I don't want to mess up the prism economy too badly, I just don't want to have to keep the actual gear anymore.