I'd have done it like Alien: Isolation, but with a different skin.
I'd have made it so that while you can kill the aliens, they're pretty hard to take down, AND if you do kill one, other aliens in the area (perhaps one, perhaps 2 or 3) will then come out of the vents and come searching for you, and there are infinitely many aliens. You can't clear areas, you can only dodge them and wait until they're gone. Soo, the only real circumstance you're gonna want to be killing them is if they've spotted you and there's no escape. The aliens that come out of the vents to investigate what happened wont really know where you are exactly.
This is, in effect, the same as in Alien: Isolation when you use the flamethrower. What happens when you torch the alien? Well, you never kill it, but it does go away. But it also comes back, and when it does, it's angry. I.e. in both situations, guns are only a temporary and last resort solution to avoiding them. Ammo of course would have to be rare, as well as the weapons themselves. Yes, killing them does make them seem a little more soft and squishy, but when the trade off is that when you kill one, you get 2, or 3, I think this won't be such a loss to the fear factor over all. And of course, they have acid blood, so shooting them at close range with anything but a flamethrower is gonna end badly for you.
I would also make the aliens in A:CM a lot bigger than they were. I'm talking like at least 7ft tall. I'd have made the lurkers basically the same as the alien in Alien: Isolation, and have it be a rare, ELITE class of alien that either pops up just by chance on rare occasion or comes down once you start killing too many aliens. And this Alien is A BOSS, tanky, smart and fast. There would be no crusher alien, that thing was stupid. Boilers however, would be more than welcome to return, they're the one thing GBX did right. Only difference is, which ones are alive and which ones are dead would be random & non-scripted.
I'd make the narrative a little different. I'd make it so that the WY mercenaries on lv426 are much fewer in number, and are effectively survivors much like ur self, rather than an army. You would be stranded on your own on the planetoid at Hadley's hope, and your objective would be to regroup with other marines, then try to take control of ops & set up camp there. You get there, you discover what a terrible idea it was and I can't be bothered to think of what happens next atm.