You'd need to add more demons to make it a challenge for 2 people, and then need to resize most areas to account for that. Who wants to be the guy in the rear while you're both crawling through ventilation shafts? Even something like that could be fun though if it were designed for coop (have demons come into the shaft from behind and in front). The size of some corridors/rooms (and numbers of enemies) will probably be an issue too. If they're a problem for coop you could just do away with them entirely. Probably at the beginning and when you go to Hell. No clue how many cut-scenes there are in Doom 3, but I doubt there's very many. But I kinda hope there aren't too many of those anyway since I like to PLAY a game and not just watch it like it's final fantasy or something. As in little movies where you're not in control. One thing that might be an issue is the cut-scenes. If one player is BEHIND the collapse when it triggers that would um, not be good. Like if the corridor behind you collapses and you can never go back that way again. The only scripted sequences that would be a problem are the ones that trigger a 'point of no return' kind of thing. If the other player isn't there to see it (the fiend coming out of the ceiling, breaking thru the door, bursting thru the wall, whatever), then too bad. Just make them trigger ONCE when the first player arrives at the trigger spot (or does whatever triggers it). I don't see how most of the scripted sequences could be much of an issue either.

Is doom co op