on the questionnaire there'd have to be a) what type do you want? and b) what type(s) can you make?
Yep, I'd definitely include those questions, along with a question for closure preferences (such as buttons, zippers, magnetic snaps, velcro). It might just be me, but I've always thought that it'll be neat to sew a zip around the three 'open' sides of the wallet...so that nothing falls out of the wallet.
Goody gumdrops...this swap might be a go! With all the customizations, we might as well consider naming this the "My Dream Wallet Swap"