The "merc" tag sounds better- I have a rough idea of what those hulls are in vanilla, but not so much In the modiverse.
I went in the faction file, set rare_bp frequency to 0, and replaced the "rare_bp" tag with "merc" in the shipsWhenImporting and knownShips sections, and after that they tend to field (and sell) what I typically see from other less-established factions that use a lot of hardware available to independents, including modded ones. More specifically I'm seeing things like the Peregrine (high-tech expansion I think), Badger (vayra's ship pack), a bunch of prv Starworks ships (which tend to appear very frequently in independent fleets by their nature), and several of the smaller Extratential Lanestate Union and Kyeltziv Technocracy hulls, to name a few.
I assume the "merc" tag gives them the same stuff you would see appearing in the random independent mercenary fleets, so I think it more or less goes with the feel you want to give the faction. Getting rid of the oversaturation of cruiser- and capital-class hulls means what they have usually has less d-mods overall, but the ships certainly don't appear in great condition generally.
I'm not sure how exactly the priorityShips section of the faction file affects anything, but presumably if you wanted a higher frequency of native Volantian hulls you could stick some of the smaller/less expensive ones there. I am still seeing an extremely small amount of native Volantian equipment in their shops, both in the case of ships and weapons, which personally makes playing the faction a little bit tedious and boring since in order to outfit ships I either have to get to a point where I can set up a colony or just wait eons to see stuff in markets (granted maybe I just have a skill issue in that I'm really bad at doing anything with vanilla weapons lmao). While they are scavengers, I think it might be fine to let them use a bit more of their own equipment since they seem to still be concentrated in native Volantian space, but I have no clue how much freedom you have to fine-tune that kind of thing.
You could also have more derelict Volantian ships (maybe also a weapon cache or two similar to DME) spawn on load the way you have those two that spawn in the Avery system, whether you just stick another couple in Avery or sprinkle them throughout a few of the neighboring systems. If you have some spawn in neighboring systems, it could also make sense to have some significant Remnant presence in those systems, given the Volantians' habit of rebuilding Remnant ships. This way, even if you don't want to change how frequently stuff appears in markets, there's a little bit more to the experience of playing VRI than just sitting around for tens of cycles waiting for stuff to appear in markets. Again, I have no idea what exactly the API gives you the freedom to do and to what extent, so just take these as loose suggestions.
Edit: Not sure if this is unintended, but the front right weapon mount on the Karambit is a medium mount, while the other three are small. Figured it's not intentional since it looks like the mount spot on the sprite is a small one (same size as the others that are all small, at least).
Edit 2: Also just noticed, it seems like the thing with the debris around Eminence not appearing may have also only happened because the mod was added mid-save in that run.