WOO! DOUBLE POST OF DOOM! Some military-grade ideas.
Snorkel:
While not a military specific device it might be worth mentioning. Basically it allows an engine to be used while the air-intake is submerged. (Presumably there’s some kind of waterproofing installed into the engine compartment as well, I’m not a mechanic.)
Armored Plating:
We’ve got Steel Plating, we’ve got Hard Plating, we’ve got Super Alloy Plating. Let’s make it worse, but with a twist. Heavier, fire-proofed, (…Is this just an issue for me?) and possibly resistant to explosions? Oh and obviously more damage resistant.
Mounted M2 Browning:
Okay, fine I’ll back down from the dismounted version. In service from back in World War 2 and still in use today. I don’t see this thing getting discontinued anytime soon so I’d love to find them on wrecked military vehicles with some ammo and be able to bolt them to my vehicles…
Bonus points for Double and Quad assemblies.
Ammo Feeds:
For not-flamethrowers, specific bins for used for holding ammo that can be fed to weapons that need it. (We can assume the necessary machinery is installed in the same fashion multiple engines, fuel tanks, water tanks, etc are connected automatically when installed.)
Mini-Guns:
…Because I’m willing to admit some people want quantity over quality even when the bullets aren’t common.
Grenade Launchers:
Self Explanatory, why not?
Smoke-Launcher:
Similar to a Grenade Launcher but rather than being fired at enemies it can be used to ‘pop-smoke’ over your vehicle. Not sure how practical but hey, someone might find a use for it.
Collision Warning System:
Not exactly military but something that came to mind. A simple message that pops up the closer you get to an object. EG it starts beeping when you come within x tile(s) of an object… I’ve run over many a gas-pumps and buildings.
Toxic Seals:
Currently, any smoke or other clouds enter the vehicle and can cause damage to the player. While this is most likely a code restriction, I have reason to think it’s realistic. Ideally you’d have to install these on every “Inside” chunk of the vehicle to prevent smoke and other contaminates from getting inside. Ideally this would include radiation as well as smoke and dust. (I’m not a Mechanic or a Coder. XD)
Global Positioning System:
While civilian equivalents exist I have no idea if military equivalents exist or use special satellites, etc. Ideally it’d be used to reveal nearby roads, sort of like a more localized, reuseable road-map. Perhaps with a chance of failure (“The GPS reads no signal”)
Run-Flat Tires (and a little re-balancing…)
Currently, tires can be armored, it might be appropriate to make them un-armorable and add run-flat tires. Heavier, harder to break, and uncommon. Comes in standard and wide tire varieties.
Emergency Medical Station:
Load it up with Batteries, First-Aid, Bandages, and Hemostatic Powder, when used it provides a bonus to First Aid skills. Perhaps a boost to CBM installation.
Surface to Surface launchers:
Perhaps a large part on the vehicle (more than one tile?) can be used to fire inaccurate attacks on single map-tiles in the same fashion as the nuclear silos. More accurate with a higher computers skill? …Hideously OP when you think about it, probably wouldn’t be able to pull them from one vehicle and install them into another, or reload it, it’s an idea. (I don’t know, I’m not a mechanic, coder, or military member)
There yah have it. Some more random ideas.