I've been toying with the idea of make your own adventure games for awhile, specially with the handheld options avaiable now.
One thing I find is your kinda force fed a little with the options
It would make a really interesting team effort if different people filled in the branches, there is a Wiki were people start the stories and other expand on them.
Personally I think I'd make it a text adventure clone, maybe expand it to a simple MI1 style gui, with pictures and text
I do have a story in mind but it might be a bit harsh.
Anyway I'm working on the system at the moment so we'll see how it goes