You may be interested in seeing how other similar projects worked out:
There's
IFWhispers, a paper-telephone-like collaborative project. Five games have been made like this so far, and the source codes are available for all of them.
There's
IF Progressive, which I haven't played yet but I understand is a progressive collaboration project. Not sure how successful it was, any of the contributors around to comment on this?
Also, famously there's
Alabaster, in which every person and their dog submitted a conversation thread for a chat with a pretty creepy Snow White. I have played it, and I thought it was excellent, but I gather there are some conversation paths which are of patchier quality than the ones I went down.
And there's the ongoing discussion about a shared world for writing some IF games in, based on
pirates with mutant powers.