I'd put a ten minute time limit on them, no multi-part stories, no canon characters or ships (including designs), no union actors or crafts people. No crowdsourcing.
I don't know if i'd be that restrictive. Runtimes don't matter, and I mean, if you're using the Federation and Klingons and Vulcans and whatnot, what does it matter if you use Kirk, Spock or whoever? The only thing there I'd agree on is crowdfunding. It's too easy to wind up with TOO much money and accidentally pocket some profit.