That's not an issue of 'realism' or suspension of disbelief though, that's more a 'game mechanics' optimization style reason. My original post is about justifying the in-universe logic for those things, not whether it is competitive with other features.
If we're talking about optimized game mechanics stuff that is an entirely different matter and part of a larger discussion I've seen pertaining to other issues (like the sheer number/options of weapons in the game as in the gyrojet thread.) Solarius Scorch probably has their reasons why that is, and I'm not really that upset over it that I feel it needs to be questioned TBH. Especially as if you know enough about the OXCE and the mod you can 'fix' those things to suit your purposes anyhow (as krautbernd mentioned earlier.)
edit: And if we still want to be pedantic 'bulky' can mean alot of things. It can refer to mass or volume, and both can be an inhibition to reflexes/response time depending on a bunch of factors (how you wear it, etc.) It may not even be a mass/volume issue but one of peripheral vision (depending on design or features - is it monocular or binocular? Is it active or passive night vision, etc.) So you can still rationalize it, especially if you consider alot of things that are added are there for aesthetics or flavor (EG that same argument can apply to the problem with the sheer quantity of vaguely similar guns mentioned elsewhere. It can add to the aesthetics or perceived 'realism' of the game without actually contributing real mechanical benefit or any benefit beyond 'what a person prefers to use.' Maybe a player doesn't want to equip their agents with M16s but would rather use AKs. Or maybe its a balancing issue Solarius Scorch intends to get to but is busy with other things. It is a big mod after all.) From a purely 'mechanics' perspective the balance issue can go the other way too - the difference in pluses or minuses is part of how the author perceives the balance. You'll get cases where not everyone agrees, which is again where krautbernd's earlier point becomes once again relevant.)
Like, you can still bring it up (that's the purpose of this thread) I'm just not sure it's a big enough issue it warrants a change to the game itself, rather than you simply tweaking it so it suits the way you feel it should be handled. I've had similar feelings about such in XCF and XP myself, but it's more about me than about the games. In other words, I see it as a 'me' problem, not a 'game' problem.