Well, if we're talking Guardian wish lists, I think it would be cool if Guardians didn't have one-way backs.
I just had someone accuse me of using marked cards earlier today, and since I'd never noticed Guardians have a one-way back, I was completely flustered. The good news is I just looked them over, figured it out, and explained.
I don't really care for gaff decks, and if I wanted gaff cards with Guardian backs, I'd just peel the backing and use one side of the double-backed card that comes in every deck of Guardians. One brick of Guardians = 24 Guardian backs you can apply to whatever poker-size gaff card you want.