I'm thinking of ways to streamline the process of making sure all of the citations are complete & accurate. This can be done cleanly for a document with a single contributor, by making sure all of the citations are accurate in your library. But for citations added by others, you can only edit local copies, which is a little bit messy. It's also much more tedious - the "auto-update" feature is not available when editing local citations.
Would it be possible to let someone take ownership of all of the citations in a document? It's already possible to add them to your library. That way you wouldn't have to edit any local copies.