So today I sat down and figured out what I think the ultimate and most awesome hypothetical Deus Ex mod would entail. If I were a modder of ultimate power, a modder of extra ordinary magnitude, I would hunker down and scream Dragonball Z style while sweat trickled down my face and veins stood out in my neck and arms until the mod I'm thinking of materialized in a blazing ball of ones and zeroes.
I know that a lot of people have very strong and well developed opinions on this matter and I wouldn't presume to question them. So I guess I should clarify that I'm just stating my personal opinion.
In order for the following not to be too confusing, I should state up front that all the changes I'd make are a combination of revision for challenge and realism, but also a 1980s schlock theme. Hence the choice of the uzi, for example, as the main SMG.
I would see the storyline as being kind of an alternative reality to the default game storyline but I'd have the conspiracy theory be the 80s cliche about Japanese corporations conspiring to somehow systematically buy out the US. The hero would be some heroic ex navy SEAL (more cinematic schlock to add navy SEALs to your game...) who after quitting the military decides to join UNATCO and fight terrorism on a global level. However, while on a mission against the NSF he learns about the eville Japanese corporate plot so he quits UNATCO and goes on a one-man vengance rage Chuck Norris assault on corporate headquarters in Japan. Which are, of course, guarded by ROBOTS, which was another 80s fear. (Robots replacing auto workers, for example.)
1.) I would revise the skill system. Pistols would become "short barreled firearms" and would cover pistols and small submachineguns. Rifles would become "long barreled firearms". Heavy weapons would be called "support weapons", and everything else would stay the same.
2.) I'd switch some of the weapons around to go with the reworked skill systems. The 10mm pistol would become a IMI uzi and the stealth pistol would become a beretta 92F. Both these weapons could be accessorized with trigger guard mounted laser sights, tactical lights, and barrel mounted suppressors, but whereas the uzi could only be loaded with regular 9mm P cartridges the beretta 92F could accept cold loaded cartridges. This would create some game balance where the beretta would be better for stealth (absolutely silent with the cold loaded cartridges) but worse for killing. I realize that silent versus not silent isn't actually what alerts enemies in Deus Ex but that the triggers are done in another way, so I'd try to work with that perhaps by making a kill with cold loaded 9mm cartrides equivalent to whacking someone unconscious in terms of alerting enemies. The counterbalance is that it wouldn't do very much damage and would only really be able to silent kill someone with a perfect headshot.
The disposable plasma gun would be a sawn off breech loading shotgun called the Boomstick. I'd change the crossbow to a S&W revolver that could accept either .38 or .357 cartridges and I'd use that as a common weapon for cops or random terrorists.
I'd have there be two sniper rifles, but I'd have to research which ones were big in the 80s. I'd have one for UNATCO and one for the NSF. The UNATCO one would be more internationalist, perhaps HK, whereas the NSF would be Americana, perhaps a Winchester Model 70 or something. They'd be similar but I feel like different weapons indicating different origins or roots would give flavor to the setting.
I'd change the largely pointless and not very fun sawn-off shotgun into a Remington 870 used by people all over the world. I'd have fun with lots of different types of shells as is the advantage with a pump action shotgun. I'd have there be shot and slug but also beanbags, which would to a tiny amount of stun damage, kind of like a long range baton, which would mostly be for fun. If I could figure out how to make certain types of rounds affect doors more I'd also add a shock lock round which would be good for breaking down doors.
I'd change the assualt shotgun to a AK47 because you gotta have those everywhere, and the assault rifle would become either a M16A2 or Colt Commando. I'd make the advantage of the latter that it would accept an underbarrel light and laser sight which would basically have a longer range or more brightness than the trigger guard mounted variant. This would be balanced by the NATO 5.56 cartridge doing a bit less damage than the 7.62x39 WP from the AK when it hits you.
The heavy weapons are a little tricky since I'd have to come up with gigantic but still man portable support weapons that work in the context of the 80s. Perhaps the GEP gun could become a Carl Gustav multi launcher. Did MGL6s exist during the 80s? If so I could add 40mm grenades and change the plasma rifle into that. Also, I suppose there'd need to be a ridiculously powerful M60 machinegun which eats all your ammo up with a little bit of use and which is extremely inaccurate considering you're firing it while standing upright.
Primitive weapons would be a lot of fun. I'd add a large Rambo compound bow! It would be like the crossbow from the original Deus Ex but it would do a lot of damage and have better range and you could still have fun with trying to hit far away targets by aiming above them. Realistic or not, I'd want to add those exploding arrows Rambo uses just for 80s veneration, but they might have crap range and accuracy compared to regular arrows. Also, in keeping with the 80s shtick, the throwing knives would become kunai, the sword would become ninjato, and the Dragon's Tooth would become a legendary Masamune blade.
I'd have right clicking for most guns bring up iron sights which would make more sense on most of the weapons than a scope. I'd have the sniper rifles bring up a scope, of course, but in order to balance them I'd have their accuracy be horrendous if you weren't scoped in while shooting.
I'd simultaneously adjust the damage values up so that headshots are almost always lethal, but I'd simultaneously decrease the accuracy of all the firearms to make them more realistic. For example, pistols wouldn't be just as good as sniper rifles, and firing while walking would be highly inaccurate.
I'd implement decapitation, which would just be a model's head turning invisible and spraying gore everywhere, in the event of a highly damaging hit to the head.
I'd make ammunition take up inventory space. No more 300 rounds of 7.62 NATO AND 300 rounds of shot shells AND 300 rounds of 10mm pistol cartridges all jammed in your coat and not taking a single inventory square.