Thinking just on the very edges of the box, a “salvage ship” is really a “mobile zero-g construction/deconstruction platform.” So even just staying in the main ship’s mission box, they can build things, modify things, and repair things as well as tearing apart and selling abandoned things. There seem to be an awful lot of undercrewed facilities in the ‘verse, so while we might expect a large space station to have organic repair and construction capabilities, in this setting probably only the largest civilian stations and the Alliance maintain those.