Hey there, I read your stories and I seriously can't choose one, they're all pretty awesome!!! I don't mind which one I co-write on, they're all great!
I'm really busy at the moment with my school work - I can barely keep up with my own stories, lol.
I don't really have time to be a co-author (maybe sometime in the future) but I'd happy to help with editing and help you out with plotlines if you like. =)