Nope, you missed nothing.
That was one of the ways I considered but the trouble with that is that I'm guessing that people in committing to the project would want to produce a unique short film, especially if it requires a fair amount of time an effort. So whilst it doesn't much matter at the screenplay stage, I wouldn't really want everyone to be making the same short film at Stage Three. If you're submitting Power Up to festivals then it's not good if there's another film with the exact same script being submitted too.
Whilst this is partly a competition, the cool part of it is that at the end you might get a product that has three different collaborators from this forum. And we might end up with a handful of shorts with a whole bunch of different combinations of members involved. In my opinion that would be really fun even if it's not as neat and tidy as cutting it down stage by stage.
But I am, of course, open to other opinions.