Well for me it wouldnt make a difference if its a driveless ship or a starbase that defends the jumppoint. My killsats are anyway just a generator straped to a freaking 500k range 20dmg particle gun and maintaince storages but thats not the point here.
I like the idea of starbases, what i wonder thought is how they are assembled. All in all you have some options there. It could be (like the Op suggested) build like a Orbital hab on a planet and then moved by a tug, or own drives or it could be assembled in space like a ordinary PDC would be on a planet. Either way works for me. For the heck of it, it could be even modular thus you tow some rump into space and later add new modules to it.
Since Spacesations would need a constant influx of maintenance-supplies, and could supply other services, why not just add another form of Hab-module that does not House workers but adds space for certain kinds of facilities like factories? This way you could build Maintenance-facilities as well as Massdrivers, Factories and whatever you have and need.
The only problem you might have is an economic one. A Orbital habitat for workers costs 100 Mercasium and 50 Boronide but provides space for 50K people which isnt a bad trade in my eyes.The thing is just that you also need 50K people for just 1(in words: one) factory in other words for every factory you would need 1 Habitat, for at 100% working shipyard 22 Habitats (1.1mill people) and so on. Without a freaking huge stockpile (or continuous production of supplies) and tons of Maintenance workers/crew i guess a armed Station with just a couple of Habs would fall appart immediately - you could (, if a station would count like a planet, ) have thought armed sats and PDCs that orbit a spacestation which get serviced by its maintenance facilities ^^.
