I don't know if you have seen this but I think its a great idea to tackle the collaborative writing process and could help the couchpress project to jump forward. ;)
I've read it and it looks rather complicated, especially as we would be rewriting CouchDB's revision system. But in saying that, CouchDB's revision system could make this possible. Will make a fork and work on it sometime.
Maxogen has realized a DVCS revision control mechanism with CouchDB in his datacouch project. Maybe this can be a inspiration for you...