Wow guys, this is a great theme, and it really works well with the focus!! If anyone wants to help me brainstorm ideas, please do!! (I won't steal your ideas)
I got this idea: Instead of saying the theme as go there and then go back, i say these are two locations named "there", and "back". In each dimension you have one player, and your goal is to collect keys which opens a door in the other dimension letting you to get more and more keys.
I'm not sure if im going to use this but ill start with this until i get a better idea (and still have time....)