If u want to create a movie with many peoples that are supposed to help u, you must have written up approximitely how the story is gonna be. U will also need to be pretty famous.
I would say that u should start of with releasing a few movies with
WoW Model Viewer+
Wow Map Viewer where only u and maybe some friends are. By doing so u cna learn how to create good movies and maybe get famous, being famous helps when trying to get help from others.
Creating movies isn't anything easy, and starting off with a movie that will engage a whole server isn't a good idea.