Couldn't sleep so I was thinking about this new Doom. They shouldn't have made it take place on earth. I know it's logical (Doom 3 was a remake of Doom 1 and this would be a remake of Doom 2: Hell on Earth). However, back in those days we didn't have the graphical power to accurately display earth in a game. So many games already take place on earth and I for one have a hard time imagining Doom on earth without losing that typical Doom feeling. Darksiders did it and although it was a great game, the earth sections we're definitively the weaker parts. Besides, as a sci-fi horror fan, I think it's a setting that's underused.
Instead they should focus on what made Doom 2 great. It was more open, it had bigger fights and a larger scale overall. I really hope they don't try to mimic COD and stick to smooth run and gun gameplay with hordes of demons. No RPG stuff please. Also, they suck at doing story driven stuff. If I were them I would take a good look at Aliens and the Dead Space games for inspiration. Make it a sequel to Doom 3 and have it start with a marine battalion being sent to Mars to investigate the distress calls. Have it take place on the ruined UAC basis and hire a talented writer.
For context I would start by focus on finding out what happened. After that, the focus should be on retrieving the gate that allows the demons to come through. You could make it that the marines have to retrieve that gate, get it on board of the ship so it can be shipped to a space station where scientist can figure out how to close it for good. Of course ending in sending you with the marines though and finish it off in Hell. This allows for a variation in settings (Mars, space ship and station (Dead Space) and Hell). I would have the game switch between moments you are alone (tension, horror) and moments you work with squads. This should help pacing. You could also use zero gravity for some awesome fights (again, Dead Space).
Drop in and drop out coop would be a given. Have players team up against the demons. Also, full fledged multiplayer, including a horde modus and of course mod support (which is unlikely due to IdTech5 it's nature). Biggest selling point would be massive fights that aren't scripted. So you got big set pieces but not the COD kind. Destructible environment, secrets and no more monster closets. Also, well lit environments (let it make sense) and dark where it needs to be. No switching between flashlight and gun. No mandatory vehicle sections please unless it works in the game's advantage.
That's what my Doom would be.
Inf - Leaving in it's torturous wake nothing but vicious, cannabalistic, mutated, radiated and horribly disfigured hordes of satanic killers!