Well, if you require a planet or asteroid for the station anyways, which is convenient because that's whats currently coded, the main thing for space stations seems to be a module system, where you can switch out modules.
Near a planet, a station might actually have fabrications to switch that out.
I would really like that, it might even allow to install a weapons module on a civilian freighter at a massive premium in mass, thereby relegating maintenance only to those weapon systems, though that obviously won't turn it into a warship.
Then, a Space station could just be switch like PDC, that's just -50% maintenance clock progression, +50% crew habitation needs, or some such, and it can't have an engine; or rather, I'd prefer it not being able to have a topspeed over a given number, say, 25 kms.
After all, a TN-"Maneuvering Thruster" might not be too bad of an idea.
After two decades, however, the frame of the station would still age, even though the modules were kept fresh; One could however deliver a new frame to incorporate those modules, given that that will be significantly lighter.
Though I personally still lack an understanding for the appeal of such large targets.
