Why not a Ri (rich) world? What about tech level? Could a TL 15 A class starport build say a TL 12 battleship of some sort? What about a TL 10 battleship? What about a world with one adjacent to it (jump 1) that has an industrial rating but is say Starport C? Couldn't they be used (assuming the right TL) to manufacture the necessary parts that the world with the A starport then assembles?
On the first part, I assume the planet is given the Rich designation because it is a biologically well off planet with populations that are small enough to be supported richly for 1000s of years, as opposed to a planet groaning under billions.
Since the max population for a pop 8 rich world would 99 million, the percentage engaged in shipyard work likely would be .1% of the population or 99,000 people. Assuming the standard still works, 1 ton per worker per year, that is in line with building and maintaining ACS ships, but not big ones.
I suppose one could argue that in desperate wartime you could go to 1% of the population engaged and that the Rich part should allow for their denizens to build quickly, and under TCS could use the 'hurry up' payments to maximize building. BUt it wouldn't be normal commercial or peacetime military business.
As for importing parts, I suppose that's possible, but it is going to be rough shipping out heavy streams of parts out of a C/D starport.
I could buy something more like a B starport IN shipping parts, but of course the local government/noble/corporate is going to strongly consider ceasing being just a supplier and go capture that build business themselves, especially since being industrial means never having to say you're sorry- er, no, means you can produce the parts more cheaply and undercut the competing shipyards for profits/market share.
I'd think that what they could build is far more a function of frequency of doing such construction and having the economy to support that construction in terms of money than it is about population or industrial status.
That is, if you have world that builds a battleship every, say, two years for the Imperium, et. al., then they have that capacity. On the other hand, a world deep in the Imperium where there's no need for such ships might not have the capacity to build them at all even as they turn out large liners and cargo ships by the dozen. The technology involved in the two isn't any more the same than it is for some shipyard to turn out mega container ships versus aircraft carriers today.
I'd think the question here is... How many large warships does the Imperium, etc., possess and of what types? Along with, how often are new ones constructed? That would drive the commonality of shipyards that could build these ships as those yards have to operate at a minimum of breaking even on production costs.
Well that gets into a whole mess of questions, much of which being OTU-related I haven't ever quantified.
Without answering that last paragraph, one could say that the shipyards that are A starports with E/F tech and IN is the effective economic/political limit as of the moment those UPP codes were determined, and shows what the Imperium has invested in doing. If the Imperium wanted more such capable systems, they would have let the contracts to fund the infrastructure and maintained it with contracts.
That may be an explanation for D/E/F TL IN worlds with C/D starports, they WERE on the Imperium military-industrial complex but force drawdowns have caused subsidized IN planets to lose their contracts and therefore not need/afford to maintain top flight ship infrastructure/shipyards/starports.
