In real life, there are good reasons for people to not go around walling themselves when facing any enemy.
Oxygen deprivation, dehydration and famine.
Implement those? Where a room completely sealed, with walls everywhere and welded airlocks turns into an horrible asphyxiation chamber if it's overcrowded? And people will think twice about using those "sandbox turtling" SS13 tactics...
I saw this in some SS13 code bases, while dehydration is still exclusive to the Fallout spin-offs.
But otherwise? Realism as a whole would be very coding intensive to implement in game mechanics.
Just some examples...
SS13 is a game where getting crushed by an airlock only causes some superficial damage...
- It maims or kill people in real life, crippling them horribly. Would do the same for a xenomorph (but will melt in the process of crushing it).
On the other hand? You can't actually electrify an airlock unless it's not grounded, and even so it would be ineffective unless you build an enormous static electrical charge in it or the person touching it is isn't insulated from the floor.
...So rigged or sensor sabotaged airlocks would be a GOOD thing for engineers to use - as a deathly trap for xenos or anyone trying to go through them.
Xenomorph acid? Is an element of sci-fi.
But considering it works like in the movies (and not in some AVP games, where you can shoot at xenos and they don't melt through a floor or at least the scenario around them)...
... fighting xenomorphs in Sulaco should be inviable.
Would cause breaches everywhere.
And fighting a xenomorph in close range, with firearms, is a sure way to get horribly crippled by acid splashes.
While a large xenomorph will not only survive some gunfire, but still slash you to death while you are melting.
If a xenomorph gets "gibbed" or thoroughly damaged to the point if it's guts spilling out - like happens in this game and in some AVP games too - it's actually a disaster for a space vessel, like portrayed in this sequence...
https://www.youtube.com/watch?v=LFN4NtioY8Q
Also? Carrying enough materials for building a very resistant wall - enough to stop a xeno - is out of question.
- Make metal sheets properly big, weighty, and costly to use for building walls, metal tables and everything.
Also make engineering methods realistic (you can't turn a metal sheet into anything in real life without proper tools ant time).
BUT...?
I guess scf-fi combat engineers would have some stuff that would at least be useful. And modern.
While still very realistic things.
( And there are some good realistic reasons for "xeno acid don't causing a breach" as I will address later.)
Here are some stuff I thought of - that is also easy to code in. (There are many things in SS13 code, that are similar to them in one way or another.)
"A thin and lightweight but resistant wire that you can wrap on insulated poles fixed to the ground with stakes (outdoor) or nail guns (indoor), and connect to a small generator - with sensors and capacitors to deliver the full charge only when a short-circuit is detected in the system, creating an electrical and efficient temporary electrical fence."
- Is another thing sci-fi engineers certainly would have. With a good power supply in said generator. And certainly a remote alarm, connected to it, by their pockets. (Of course a xeno can rip it easily, and get only a little of electrical burns - but maybe no stun at all. Idea here is a temporary hindrance, with some damage to the trespasser, instead of a solid barrier - with more very realistic tactical elements.)
"A thick kevlar-aramid composite tarp, bullet and fire proof to some extent, that you can attach around an opening (between walls, with a nail gun) or resistant poles attached to the ground (same poles from the above item) for filling gaps and providing coverage."
- Would at least require the xeno to climb or rip through it, and be some sort of obstacle, while actually not that tactically good because it blocks vision and marine gunfire - like a wall does - however it's very realistic.
"Area movement multi-mode sensors, with receivers configured to them, that also receive wireless tag information from IDs, so it can warn the engineer with the receiver if there is movement by that area - and if there are marines there or not. And even what marines are there. (Receiver can be configured.) - It may even can receive data from colonists IDs too."
- Certainly some thing combat engineers would use, specially on the case the troopers must cover a big area with small forces. Also very "sci-fi" friendly and quite a thing the USCM would have for helping to deal with typical rioters or invaders in a colony.
On coding part? Nothing more than the SS13 movement sensor with an ID check and signaler in it.
"Inflatable, easy to deploy tents, that can be covered with tarps to give them better resistance. (Can use the same tarp mentioned before.)"
- Obviously because USCM sometimes would need to land and build a FOB in remote places.
Specially if a colony is taken over by hostile fighters, well armed pirates or rioters that planned the thing very well, where landing close to it would mean getting a portable missile launched on the drop ship.
Another easy thing to code. (AOE building methods like the ones used in shadowling hatching or the lavaland shelter, plus the ability to add the tarp to the inflatable walls. - There are even already those walls in the game, only they aren't like something USCM would have and are far away from realistic.).
...
Now on the xeno acid, breaches, and corresponding engineering abilities?
Is of note that in SS13 and even AVP lore, space stations or combat ships look poorly designed for standing against meteors or enemy gunfire. (Have in mind that Sulaco literally had explosives and fuel by the cargo, with no decent firefighting systems...
http://avp.wikia.com/wiki/USS_Sulaco )
But in SS13 specifically, breaching is exacerbated on purpose - and this is in tune with the engineer's wall and floor building abilities, and the idea of "a horrible metal death trap masqueraded as a space station".
"Nerf", remove or change the breaching ,mechanics for your game?
And you can safely remove any "superhuman wall building ability" the engineers might have without causing negative impacts.
Destroyed floor could lead to another part of the ship, or to a "deep hole in the structure" where a player may fall and get damaged in but can climb back instead of directly to the space.
External hull walls could be two squares thick - and stand almost any abuse - with even a system to spill a sealant when damaged.
Also?
There are no reasons for a combat ship to have that many glass windows - exactly the same logic behind war submarines having no windows too when compared to sea exploring submarines (windows break easily and can't be easily fixed).
There is also no way a combat space ship would place command's bridge in the front.
A war submarine diagram is a good reference for real-life design that would be implemented.
Notice that the control room is in the middle.
As I said? Reality is hard to implement as a whole. - But certainly not impossible.