This is a pretty hefty contest, so it might take some time to gather the funds to make it viable, but...
A film-making contest in several stages

1. Writers write and submit 1-4 page scripts using 1-2 actors based on the prompt (and set in locations that can be found everywhere) within post payout of the contest announcement post (via linkdrop in the comments to their own script post on their page)
2. Everyone in the Over 20 Club gets to vote on which script moves forward (by upvoting the scripts in the comments section). Winner gets 25SBD
3. Actors record and submit videos of themselves doing the scenes in the appropriate settings. (By posting the videos and dropping a link to them in the comments section of the winning script announcement before post payout)
4. Everyone NOW in the Over 20 Club gets to vote on which performances are used (by upvoting the comments). Winner(s) get 25SBD each.
5. Editor-cinematographers submit finished products (including footage they might have to shoot themselves, like establishing shots, inserts, or just pretty scenery) (again, submissions by posting and dropping a link before post payout of the previous announcement).
6. Everyone NOW in the Over 20 Club gets to vote on their favorite (same method as before). Winner gets 25SBD.

There'd be some legalese in each step that both protects the rights of the submitters and @freewritehouse. Also, I'd be happy to write some best tips and practices for each stage (especially for people submitting performances, they should submit some different angles of themselves doing it so the editors have something to work with... not too much, though, as it should still be pretty quick and dirty.)