I think heavy weapons would definitely require some consideration about how to implement, since their high power is usually paired with downsides - equipment is heavy, ammo is rare/expensive, etc. - that would make them really tough to use in Underrail.
That's the point of heavy weapons, they're LOUD and POWERFUL, but a very heavy and costly, as one wise russian said "It costs 400,000$ to fire this weapon for 12 seconds". Or in RPG case, you basically have a sniper rifle that shoot very powerful grenades.
About your idea of removable components, it's sounds awesome and probably not so hard to implement, it can be done by adding mini-inventory for some armor and by adding there specific items you can change stats or add new skills/passives. It irked me a little when you couldn't just replace armor plates of your tactical vest.
I guess my idea of mods can be too op for this game, I just really like how modular kerberos squad armor is. Their armor not only have rebreathers an NV, but also have a backpack that stores radio equipment, oxygen tanks and ammo belts for their machine guns.
And I thought about how new mechanics can make this work. If armor and weapon mods get expanded and enchanced then there will be new engieneering direction for builds that can replace psi or compensate for weak weapon skills.
My problem with psi is that I don't want to use it on weapon oriented characters and try to replace it with craft, but psi is too effective and resources/exp cheap to pass it, and with buffed craft system I can replace psi with it and still have a quite viable build. But I'm pretty sure that Styg's gonna rework most of psi.
