Let me ... amend ... my preliminary notions that I advanced in the
Arcologies thread previously.
And yes, this will affect certain other assumptions that I've been making thus far about the best way to organize these things.
Let's look at this from a hull code requires minimum computer model standpoint, and I'm going to be using LBB5.80 for this (because it's what I have access to and CT is the easiest to "convert" to any other editions of Traveller).
600 tons (hull code: 6) = model/1 required (TL=5)
1000 tons (hull code: A) = model/2 required (TL=7)
4000 tons (hull code: D) = model/3 required (TL=9)
10,000 tons (hull code: K) = model/4 required (TL=A)
50,000 tons (hull code: P) = model/5 required (TL=B)
100,000 tons (hull code: R) = model/6 required (TL=C)
1,000,000 tons (hull code: Y) = model/7 required (TL=D)
Now, if we tie those hull size breakpoints in with the
Shipyard Construction rules that
@Grav_Moped found in MgT2 High Guard, what makes for a sustainable combination of modular component sizes to work with for various purposes? Also, let's assume that Boughene Station was built "on the cheap" by General Products to be adequate to needs (300 years ago) and everything has simply grown from there.
So if you start with a 100,000 ton hull Jump Tender capable of transporting a 50,000 ton hull module built elsewhere (let's say Efate for convenience of conversation) you can have that 50,000 ton secondary module be a shipyard capable of construction (type A starport) with a 20,000 ton build capacity occupying 40,000 tons of the 50,000 ton secondary module.
100k ton Jump Tender + 50k ton Starport Module = 20k ton type A starport shipyard capacity
Jump Tender must be TL=C for model/6 computer and Starport Module must be TL=B for model/5 computer as minimums.
Everybody with me so far?

Up to this point, I'm just repeating what I wrote in the
Arcologies thread previously.
The part that I would want to amend is that the additional modules for population housing (staterooms), commercial districts (auditorium spaces), industrial districts (workshops), research districts (laboratories), warehouse districts (cargo), fuel refinery/tanker (fuel reserve and purification plants) should actually be constructed in 10,000 ton hull modules (code: K, requires model/4 computer, TL=A minimum)
BECAUSE those 10,000 ton hulls can actually be constructed locally in the Starport Module with its construction capacity for 20,000 tons. That way, any additional modules for population support do not need to be constructed elsewhere (like, say ... Efate) AND the annual maintenance for those extra modules can be performed locally (usually only 1 at a time leaving 10,000 of starport capacity remaining for any other commercial and/or IISS traffic).
However, a single Starport Module would only be capable of performing annual maintenance on about 20 other modules per year while still leaving reserve capacity for interstellar trade and commerce. Additionally, the Starport Module would need to be taken, by the Jump Tender, back to Efate every year so that both the Starport Module AND the Jump Tender can receive their annual overhaul maintenance. In which case ... having only a single Starport Module is going to become a pretty serious problem, logistically speaking.
Solution?
Multiple Starport Modules
So a 10,000 ton Habitat Module mostly full of staterooms is going to have enough room for about 2000 staterooms (8000 tons displacement). For a population of 600,000 permanent residents, that's going to mean a minimum of 300 Habitat Modules of 10,000 tons each just to accommodate a population of 600,000 people.
300 Habitat Modules receiving annual overhaul maintenance locally in the local starport facilities will mean that at 2 week per annual overhaul, each 50,000 ton Starport Module would be capable of overhauling 2 modules of 10,000 tons each every 2 weeks or 52 Habitat Modules per year if that Starport Module is solely dedicated to supporting station maintenance.
So with 300 Habitat Modules needing annual maintenance, a minimum of 6 Starport Modules would be required to service local maintenance needs locally on a rotating schedule (because the Starport Modules will need to be taken offline for transport to Efate for their own annual maintenance schedules).
In point of fact, having 13 Starport Modules would mean that a 4 week rotation could be set up per Jump Tender (1 week transit to Efate at Jump-2, 2 weeks annual overhaul maintenance, 1 week return transit to Boughene at Jump-2) meaning that in point of fact there would be 12 Starport Modules available at all times, with 6 of those fully occupied with annual overhaul maintenance of just the 300x 10,000 ton Habitat Modules at all times.
1x 100,000 ton Jump-2 Tender supports up to 13x 50,000 ton Starport Modules maintaining up to 600x 10,000 ton Modules (various types)
So the Jump Tender and Starport Modules need to be on permanent rotation for annual maintenance at Efate ... but all of the other modules receive their annual maintenance locally at Boughene. Any "surplus" Starport Module capacity is used to service interstellar shipping needs.
This means that ideally speaking you would want to have:
1x 100,000 ton Jump-2 Tender
3x 50,000 ton type A Starport Modules (20,000 ton capacity each, construction and maintenance)
10x 50,000 ton type B Starport Modules (20,000 ton capacity each, maintenance only, no construction)
500x 10,000 ton Modules (minimum 350 habitat stateroom modules, 660,000 sophont capacity in modules not undergoing annual maintenance, plus 150 other types constructed and maintained locally)
Total displacement = ~5.8 million tons for the entirety of Boughene Station
Done that way, "local industry" can expand Boughene Station on an as needed/can afford basis depending on the in-system economy and the only "reliable" trade deficit would be with Efate for annual maintenance of their Jump Tender and Starport Modules (and needing to replace all of those every 40 years).
The 10x type B Starport Modules are completely dedicated to maintaining the 500x 10,000 ton Modules that make up the bulk of Boughene Station, so they're purely for local overhaul maintenance needs.
The 3x type A Starport Modules are mainly dedicated towards interstellar starship support and ongoing construction of replacement 10,000 ton modules on an attrition rollover schedule are the reason why Boughene has a type A starport rating at all. Three times a year, every year, only two of the type A Starport Modules will be at Boughene station, while the other one has been removed for transit to and from Efate for annual overhaul maintenance there, and one of the remaining two will be fully engaged in construction of replacement 10,000 ton modules to keep the space station from aging out over time.
Because Efate is TL=D the type A Starport Modules (capable of construction) are built to TL=D standards.
The type B Starport Modules can be built to whatever tech level best matches the 10,000 ton modules overall (minimum TL=A) for cost savings or could also be optionally built to TL=D standard (smaller fusion power plants are cheaper).
Ironically, the above setup is approximately "right sized" for a space based population of 600,000 permanent residents (plus 60,000 additional visitor traffic) with sufficient light/heavy industrial and research/commercial capacity to be somewhat self sustaining over the really long haul. In order to expand the population even further (to over 1,000,000 and reach population code: 6) would require an entire second space space station (1 Jump Tender, 13 Starport Modules and 500 Secondary Modules).
No wonder the government type is Self-Perpetuating Oligarchy ... because
cash rules everything around me in the Boughene system.
Also, since the system remains in the Non-industrial category due to "low" population (code: 5) it makes perfect sense that the locals are attempting to improve their resource extraction potential on Boughene itself to finance further expansion and settlement opportunities in the system, improving the economy. However, that next step in expansion is going to come at a pretty steep cost with the need to add a new Jump Tender and more Starport Modules before the population can grow even further beyond the current 600,000 in 1105.
Also, side note ... the annual overhaul maintenance schedule would mean that permanent residents can expect to move/migrate their quarters every single year when the module they have been inhabiting for the past year is due to go in for annual maintenance (which requires everyone to vacate and "take their stuff" with them so maintenance crews can do their jobs properly). Consequently, "ownership" of individual staterooms would be relatively rare (basically for the wealthy only), with most people simply "renting" stateroom quarters from the owner of a specific Habitat Module with move in/move out clauses in their lease agreements covering their move/migration to another Habitat Module when the current one needs to be put into drydock for annual overhaul maintenance.