One aspect I will probably implement is user-controlled combat NPCs. Since there will be wildly inconsistent power levels and god-tier abilities, player vs player or gm vs player duels will be a nightmare to manage, so instead, each co-writer will also be controlling any NPCs/monsters they fight with so that they can write out the battle scenes as if doing it for a novel. Basically, what that means, is that at the beginning of any combat situation, I will throw enemies at any participating characters, give a little info card at the bottom of the post saying what the enemies are capable of and how difficult the fight should be, and then the co-writers will take over that fight their characters are engaged in. 

So, if it's a group combat, I will just throw out a bunch of enemies and then co-writers can claim targets in OOC like, "Okay, I'm going to have John focus on the ogre," or "Jack and I discussed via PM that we are gonna double team the troll."