But I'm curious what kinds of hardware limitations to do you grant your private owners and companies to protect themselves? Limit vessel size? What?
I've always gone for "soft" limitations. That is, there isn't some stringently enforced Imperial edict which spells out precisely that A can only install B aboard C while X can install Y aboard Z. Instead, the limitations
IMTU are primarily created by issues like cost, availability, parts, maintenance, operations, training, control systems, and so forth.
Putting it another way, Cap'n Blackie isn't going to have a TL-15 PAW turret mounted on
The Running Boil more because he can't afford it, can't find someone who will sell him one, can't maintain it, doesn't have a crewman who can operate it, doesn't have the control systems for it, or other such issues and less because Redtape Q. Bwap of the 117th Ship Weaponry Auditors Corp won't stamp the proper forms.
These "soft" limitations doesn't mean that weaponry aboard ships doesn't generally scale as ownership scales from individuals to corporations to governments. And it also doesn't mean that starport authorities of all stripes across Chartered Space won't look very closely at certain ships, require some to some to remain in orbit, and even require others to stay further out.
IMTU and in my campaigns, I categorized ship weaponry into 4 classes whose boundaries definitely "bled" into each other. These categories were a direct result of our adoption of the
HG2 combat system for our campaigns'
Mayday/LBB:2 sessions.
The first category is single weapon/single turret batteries. Most civilian small ships fall into this category as do most PCs' ships.
The second category is multiple turret batteries. Most corporate and paramilitary ships fall into this category while PCs/NPCs could "upgrade" their ships in.
The third category is weapon bays. Government and some corporate ships are in this category.
The fourth and final category is spinal mounts. While there are exceptions like Oberlindes'
Emissary, government ships primarily make up this category. Spinals
IMTU are pretty much the only weaponry you won't see in civilian hands.