Let me clarify.
There are two kinds of troops transported aboard Navy vessels, ship's troops and, for lack of a better term, 'troop contingents'.
- Ship's troops 'belong' to the ship's complement just like the spacehands do. PFC Alpha is assigned to 1010th Marine Regiment and the Regiment is assigned as Ship's Troops for the 12th Battle Squadron of the Spinward Marches Fleet. Alpha's battalion is specifically assigned to the INS Outrageous. Able Spacehand Bravo is likewise assigned to the Outrageous as a gunner's mate. While they arrive at their duty stations by administratively different routes, PFC Alpha and ASH Bravo still turn wrenches on Outrageous' Missile Bay 3 and both are permanently part of the ship's listed complement.
Alpha is under the orders of both his Marine Force Commander and the Captain of Outrageous, though the Captain will likely route any orders to the Marines aboard through the Force Commander. Bravo is under the orders of Outrageous' Captain, and is not normally in a chain of command that includes Marines.
- Troop contingents are Army or Marine units being transported to their deployment zones by Navy ships. They are 'cargo' in the sense that they are temporary occupants of the ship's troop berthing. Once the ship reaches its destination, the troop contingent and all it's equipment will permanently disembark the ship for whatever campaign they're assigned to fight. At no point are troop contingents subordinate to the transporting ship's captain other than safety matters.
What I'm saying is that troops of both types ought to have the same berthing arrangements as the naval spacehands AND that troops of both types require space to train and maintain their equipment in addition to enough common space to mess and recreate. Why does a spacehand rate the comparative luxury of having just one roomate when troops are wedged into barracks stacked three to a bunk tier?
So we agree that either transported Army troops, "Marine" troops who are part of the ships complement as security/gunners and Marine regiments that are part of a warships permanent deployable complement should all be treated equally.
So your issue seems to be is assigning troops to barracks rather than the type of troops they are. In your bunk it makes little difference if you are in a room shared with 2 or 4. When you are standing your watch (either in the gunroom or at a crew station) it also makes no difference as you are not in the accommodation. So we are really talking about the 8 hours or so of "private" time.
I do see a fundamental difference between regular crew who stand regular watches vs troops that only stand to in emergencies (bearing in mind in an emergency the regular crew will likely stand too as well).
A unit of troops will tend to socialise as a group. They tend to operate as a team and so sharing accommodation is probably beneficial for the team. Whether that is a 4 man bunk-room or 5-man (depending on your doctrine) you are spending all your time with the other people who will be looking out for you on your deployment. You will socialise with the broader unit, but that very close relationship with your squad-mates will have a beneficial effect in combat. The same is true to a lesser extent regarding the ships gunners who will often need to coordinate fire arcs. I therefore also accommodate dedicated ships gunners to barracks. The fact that a Gunner is paid the lowest of all crew is also indicative of the level of accommodation they could expect. I tend to assume dedicated gunners spend the rest of their time as deckhands.
In contrast crewmembers who are not required to react instinctively in relation to the actions of their squad mates but whose job might require disagreement and discussion to resolve issues, might benefit from spending less time in the close company of others. If you and another Engineer have had a robust discussion about the solution to a problem, you might well need a place to distance yourself so you can regroup, get some perspective and be able to compartmentalise that disagreement in order to work together successfully the next shift.
We also gloss over how crews actually perform their function. It is not unreasonable to expect many of the technical crews to have facilities in their accommodation to work independently (away from distraction). That likely includes a desk space and a terminal of some sort and possibly a backup crew station. If a gunner needs some alone time to practice that is as easily performed in the gunroom or turret since it is only in use in an emergency.
Crew accommodation has become more pragmatic through the versions. Sharing a stateroom was the first step. Now with Cabin Space, Barracks and other accommodation we can revisit the general crew requirements so that they reflect the needs (and privilege) of all crew, not just troops.
Training, and maintenance and storage of equipment are covered by other components in High Guard. If you want to do more than field strip your side arm, you need an armoury or workshop. Training will be via the same mechanism that the other crew have access. By the time it becomes an issue your barracks will be sufficiently extensive that the 10% recommended common space will be able to handle it. You could fit a tube range in 1DTon if you chose the correct place to put it.
