Funny you mention Callisto; every summer (so like right now) I get back into modding SO. Been playing with mat, meshes, ship files and found a few interesting tidbits. There's in total 4 space station like Confed/human capships in the vision engine; the Comm Relay station (crelay), Callisto base (cstarbas, I think), from WCP , then the Confed outposts, Talos Luyten(?) and Krieger(?), followed by Ella Superbase.
Now, I'm on my phone not my computer so I can't give file names and facts with confidence but I know either the outpost' s or Ella's actual ship file is named *drum roll* callisto.iff!
Not only that but the VDU image for Ella was once Callisto's I think, and the Outposts have their own unique VDU image but it's never used it just uses the comm relay one. I say this because when I re-added the Callisto base to SO it had the Ella icon. And the outpost one I found in the game files. Also the spinning ring on the outpost has a destroyed mesh+texture but it's not a targetable or destroyable component.
Found some other gems in the code. Some stuff Quatro stumbled on whilst making that model viewer but other things too. A low poly Comm Relay station, even more low poly than the further LOD model, two different temp Midway models, one further along than the other, a temp aceship (Devil Ray) which is really just a textureless Manta, that planet and moon model that was super low poly, and the planet terrain for ground missions.
Since we're on the subject of the Midway being next on your hitlist I might dig up that temp Midway model and take screenshots. It's actually got more details than the final model in some areas that you might want to incorporate. The Midway is hands down my favorite capital ship design (both in premise and how it looks) so I'm super looking forward to your recreation.