I havent played Doom III so Idk if this is in it, but realistic healing animations like in Far Cry 2. I mean realistic as in you see your character pull out a shard of metal from his arm, or wrap a bandage or at least pop the pill bottle.
Would be pretty cool, and add to the 'nasty-o-meter'.
That's actually not a bad idea. I remember once I survived getting my car blown up, but I was in bad shape so I went to heal, and I had to pull out
a gigantic length of metal I'd somehow been impaled on. Only problem I can see with this is that the medkits have always been "walk over the bastards and feel better before the Baron of Hell finishes disemboweling you," so the animation would have to be either after the fight's over, or else the demon would have to patiently wait while you heal yourself.
Now that my brain's unbroken, so to speak, Hairdo Galosh Jam, I'll try to explain exactly why your idea drove me into a state of shock.
First off, How in the hell would Doomguy ever, I mean ever, be involved with hell? From what we've heard so far, DOOM 4 isn't a sequel to DOOM 3. So that means that the only Doomguy coming before DOOM 4's Doomguy is the badass, tough-as-nails, run 57 kilometers per hour, space marine from the original game. Who canonically killed the icon of sin
three times over, if The Ultimate DOOM is canon. Even if it's not, he's literally killed an entire ARMY of Cyberdemons and Masterminds just in DOOM 2 (there goes your idea of improved Cyberdemon production, considering how many they churned out in the sequel. If they made any more, you might as well play http://www.youtube.com/watch?v=O_GM3xjDVVo). Even if he did want to conquer the planet, Hell would have nothing left to offer him. He'd have to do it on his own (which he may well be tough enough to do on his own, but that's beside the point).
As for demons using guns... look at the imp (well, google up a sprite of him, at least). That poor bastard's got three fingers in the first two games, and I'm not sure he could hold a gun in the third even if he had five, seeing as he's got those claws. He likes his fireball just fine. As for demons with guns... that's what they possess the commandoes for. If they want to, they can possess more. You clearly have never fought a firing squad of chaingun commandoes. After you do, you'll never ask for demons to have more guns.
Also... there's the fact that they already DO use guns. The Mancubus (the morbidly obese one from every game except the first one) has a rapid-firing fireball launcher (of fire). Cyberdemon obviously has a rocket launcher. The revenant has homing missiles. This leads me to conclude that the demons that don't have modern weapons simply don't want them. I really don't see anyone strapping guns to a cacodemon ( I guess it'd throw off it's flying balance anyway, if I had to give a reason other than the fact that it already spits out fireballs). Barons of Hell definitely don't need any to kick ass (the Hammer Bros from the first game, anyone?). My conclusion is the only thing they could really improve is strategy. As someone once pointed out, the only thing the lost souls would even HAVE going for them would be strategy; they're small, highly mobile, but they can't do anything unless they're up close, and even then... it's just, you know... ridiculous for them to charge right the [censored] at you. But they do it anyway! Same with the imps, even in DOOM 3; they just run at you. They know they're weak as piss, they've only been killing scientists up 'till now, but they charge you anyway!
That'd be a really revolutionary step forward for the DOOM franchise; monsters with semi-brains.