Just some random musing about game design.
The health packs, or miraculously curative items of quickly-digested food, that litter most FPS and similar games are a necessary corollary to the kind of combat presented. You are usually mowing your way through a lot of mooks. And often they have similar weapons, or at least comparable skills -- so it actually takes some effort to defeat them -- and it doesn't feel realistic if they don't score on you a bit. But because of the sheer number of enemies, to make it seem you are actually in contest and in combat you need to take multiple hits. To survive them, no single hit can be crippling...and healing can only be another room or two away.
Several unfortunate things happen because of this mechanic. A "charge right in" player style as often as not -- because it is safer to run to the next health pack, then to linger trying to take a smaller number of hits to begin with. And in those times the game actually puts pressure on you by withholding health packs, so accustomed are you to refreshing your health at frequent intervals, it doesn't feel like a challenge; it feels like an unfair imposition.
The older "recharge while resting" mechanism had its bonus, but then you either get the player feeling unfairly put upon because mooks keep re-spawning and spoiling their beauty sleep, or the game turns into "play for five seconds, retreat to recover hit points for twenty" and that is a boring way to play.
And those same FPS play a nasty game of "you can't take it with you" as well. Even though you have no problem carrying eighteen different weapons on your back, out of the room full of crates you just opened you can only remove and carry off ONE magazine. You can't stick the others in a pack (although I've spent a fair bit of effort in Half-Life2 throwing spare magazines and health packs in front of me down the corridors!)
Which means that even if you stumble into a medical dispensary, or a fully-staffed hospital, or have a "after three weeks of recuperation back at your base" cut scene, you can't get your base health any higher than the same number you achieve seconds after running through a machine-gun volley and then across a couple random health packs found lying in the street.
Well, I'd love to see an FPS game with hit points being roughly conserved for the length of an episode, chapter, mission. Like the old RPGs where you would have to rest up at the inn overnight in order to reset all your hit points and manna. Sure, there might be a bit of first aid, or special game mechanic like a healer character or something similarly magical, but basically, you'd start each "mission" or major chapter fresh.
And you'd get mostly cosmetic injuries if you were lucky. If you were less lucky or careful, the injuries you'd take wouldn't be just numbers off a hit point total. They would reduce your effectiveness in various ways. But this wouldn't feel unfair because the level design would compensate; it wouldn't put the stuff where peak endurance was needed right at the end of the level, but instead play towards other strengths, ones that weren't effected quite so much by the accumulated injuries.
And a lot more of what you took would be portrayed as scrapes, bruises, cuts; John McClaine stuff. The old "bullet through the shoulder" would be rarer.
Which means that even though the mooks could be throwing the same weight of rounds at you -- suppressive fire is a thing real armies do -- you weather this not by taking five or ten hit points for every round that hits you, but by almost never getting hit in the first place.
Which is a problem. In real combat, suppressive fire works, and teamwork and flanking movement is usually necessary. When you are on your own, extensive use of cover (or if you can't get that, concealment). And stealth games are a thing, but we'd like to have a combat game too and doing it this way either requires way too much of our friendly AI's, or is too slow.
Of course, one of the reasons stealth and use of cover is so slow is, well, historical. Running across the battlefield guns akimbo is the default setting, and special enemies were introduced that required less-used mechanics...and all that boils down to making moving in a crouch slow and difficult.
Plus the basic ways of handling the game universe that are down behind the code treat your character as a bounding box. Crouching is implemented by making the box shorter. The engine may be able to draw a line of sight to an actual 3d model of your character, but collisions with scenery are usually handled with the bounding box. And there is no simple way to represent to the player the ways a physical body interacts with cluttered terrain; the scrambling, twisting, elbow-crawls and low rolls to get around and between objects while maintaining cover and concealment.
Still, I suppose you could rethink the movement paradigms. Just as "sprint" is a special key and often has conditionals (as in, you can only move faster than a walk for a short period of time), "crawl" could be treated not as it is currently -- having to hold down a crouch key and awkwardly press the movement keys at the same time -- but as an alternate, or even a default, movement mode while under fire.
But the biggest problem is that, really, you need to reduce the number of mooks. There isn't a good way of realistically dealing with hundreds of people shooting at you, and have it still fun to play. Well, other than the Pac Man arrangement of easy health and convenient ammo dumps we have now.
If you reduce the number of mooks, the biggest problem is that you reveal the shortfalls of the AI more. Which is another way of saying each mook needs a lot more scripting. And they are of course more dangerous now. Which really means that instead of hundreds of mooks, what we are fighting is a series of boss encounters.
Each soldier that is ahead of you is, not just a possible five or ten hit point penalty and a place to grab a fresh ten-round magazine, but an individual encounter. Set up the same way bunches of mooks are set up in many existing FPS; the group of soldiers right around a corner with a stack of barrels or a ventilator shaft that you can use to tackle them other than head-on. Or the squad that spawns right behind you in a dead-end hall forcing you to engage at point-blank range.
But this would still take longer in level design for the same amount of play. Because ten random mooks in a room will average out the flaws in the AI a little bit and they won't look completely asinine. But a single elite in the same room -- a boss mook -- needs to be much more carefully scripted to feel like a realistic encounter.
And because of the no-healing-until-end-of-episode arrangement, the level designer would also have to be more careful not to create situations where an injured player has no ability to complete, and their only chance is to retreat all the way to a much earlier saved position. And they would also have to work at making climactic challenges to each level that allowed for the range of injuries sustained to that point, without nerfing it for the more successful or careful player.