Shouldn't it be more common with collabs that kind of follows a story? Or any at all, I can't remember any from the top of my head.
Like, you just have story that either already exists or written by the collab participants, then everybody animates a chunk of the text (while following some guidelines that is common for all parts so that the transitions between the different parts go smoothly).
Another idea might be to make a game consisting of a few smaller games, with cut scenes and some kind of plot. This could involve all kinds of people on here: writers, voice artists, animators, and programmers..