One of the biggest sore spots of any players of (classic) Traveller are starship computers. Even after explaining that jump plans don't compute themselves and maneuver drives need careful minding while they break the laws of physics they seem to be too big for what they do. I'd like to weigh in on the subject.
Starships are modular, even the streamlined ones, to a great degree. That is you can switch out drives and generators and even take apart staterooms to rebuild your quarters deck the way you want. Married couple with high passage? Push those two staterooms together! Set them up as a pod hotel if you like.Similarly ships can keep swapping out drives and such as they wear out to extend their useful life. there are never enough ships after all.
Winchell Chung, Raymond McVay and many many others have brought up a legal query: if you have a ship you an replace everything on is it still the same ship? This is better known as The Ship of Theseus. Legal types like to worry about this stuff and so do banks that mortgage the darned ships. If you have a bunch of ferrous hulled far ranging FTL Frankensteins flitting far and wide, how do you identify them for legal purposes. What happens if a captain skips with his ship and puts his mortgage money into pimping his ride? When the ship calls at a port the authorities try to seize it but wait ... the ship they were looking for could pull 1 gee and this beast can do3 gees easy. The swiped ship similarly had different cargo and fuel capacities. Does the bank president yell, "Curses foiled again!" and slouch away twirling his or her mustache (I'm equal opportunity, either or any gender can be a villainous prick)?
Enter the big-assed Classic Traveller computers from a game conceived when the only mobile communications device you'd carry would be a beeper that fit in a backpack. For this reimagining consider it more of a group of core systems tied almost inextricably into the keel (or whatever you call it on a spaceship). That my friends identifies the ship for legal purposes. Try to rip her out and unless you have a Class A shipyard you'll be likely to be left with a junked ship. And first rate shipyards have many nosy inspectors monitoring such upgrades. Buying a new computer requires a change of registry, notification of financial institutions and probably DNA samples ("You aren't sticking that chainsaw with scalpels in my mouth!" "It doesn't go in your mouth. Lrt me just twirl my mustache a bit first.)
This might justify the original High Guard system of restricting maximum hull size by computer model. It's not so much the computer as the control core around it. It needs to be a certain size to regulate the systems on bigger ships.
One more little catch I haven't been able to iron out. Electronics have a finite lifespan. So undoubtedly the computers have modular elements in them as well. Removing and replacing a whole core every forty years or so (right after you make your last payment!) is just cruel. How much of the computer d you replace before it's no longer the same computer?