Well, if Lemur ever gets around to making MP games that have mutliple maps, I don't see why you wouldn't be able to script in a mass co-op game.
This would take a while, though, since it would need to have all dynamic objects updated perfectly on everyone's computer, as well as the ability for the AI to distinguish between each player. They would need to CHOOSE a player target, and stick to THAT target on ALL computers currently playing. That's not the way MP works right now, so I wouldn't say that it'd be happening anytime soon.
The one and only,
~PlystirE~