If you put it in orbit of one of the moons, you could create a maintenance base on that moon use the existing maintenance modules. I've also considered some type of very large, expensive "self maintenance" module intended for bases. I just haven't found a plausible mechanic to prevent its use by very large warships.
Steve
Why would you want to dis-allow this for big ships? If you make it big enough it would only really be of use in
really big ships, coupled with a huge size, massive amounts of crew (One of these monsters would clear your pool of trained crew available in one fell swoop and still fall short, you would need a huge dockyard and a long, long old time to build it. Leave it in as a possibility just make the negatives outweigh the positives. I say this as the first thing I thought of was building a new class of armoured tug to pull such a station around. I recently read (on your recommendation Steve), the Galactic Marines ennealogy, and on book 7 (I think) they used a station with tugs to transport the fleet to the nearest stargate, by book 8 it had its own engines which they used to reach the Galactic core.
You could make the component the engine itself, used for station keeping - this then opens up the possibility of a tech tree so you'd need a better type to hold station in gravimetrically dense areas such as around warp points or in black hole systems.
Either that or you only allow it to work when the station is in place (same as orbital terraformers), and linked to a target planet - so for instance a low tech version on a station that will link to terrestrial planets (like an orbital habitat module is assumed to have all the infrastructure to transport its workers to and from the surface), the component has all the kit required to mine, transport and convert relevant raw materials from its linked target planet for use as consumables, as the tech gets better new self maintenance module designs become available that can extract what it needs from deep space, warp points, even wormholes at the top of the tree.