My idea was to rewrite Star Wars episode one, and actually make it something people would want to watch.  We would have to run a Titanpad to do the Collab in, and post every scene or so.
Basically, as long as we end up where EP 2 starts, with:
Anakin being Obi-wan's padawan, and in love with Padme (preferably in a less creepy way than "I saw you when I was nine and still have a crush on you 10 years later.)
Everyone in the same positions in their organizations (jedi/senate whatever)
etc.

it will be fine.
Everyone would control one or more characters, though preferably no more that two main characters per scene.