This isn't strictly Traveller, but a thought popped into my earlier. Practicality aside, I thought that maybe a Dyson Sphere could be created in space on a very small scale, on the planetary size. The inside is where a continuous ever present power source fuels energy needs. The top side is like a giant planetary spaceport and sealed city; I was thinking something along the lines of Coruscant like with airlocks for vehicles and various species to enter/exit the habitable insides of the city.
Power will be relatively low - Jupiter emits around 4x10^17 watts, compared to 3.85x10^26 watts for Sol. Current average power consumption on Earth is around 1.5x10^13 watts, so you're talking about power generation about 25,000 times what we currently produce on Earth, as opposed to 2,500,000,000,000 times for a Solar Dyson Sphere.