Yeah, you're right. So is the Executor of course.
It still confuses me, given that Home One is also in the position of being nothing more than a subclass (It's an MC80). So that would make it a MC80 'Home One' and we still don't know the sub-designation of that (by all indications there isn't any, so we'll have to see how FFG tackles it). It would be like we'd have to have an M1A1 mk.2, it's not something we see.
Anyhow, I'm still pretty convinced on the 13.5km measurement, but it's true, we're talking about something that's only 2/3rds the size at modest, 1/2 the size at large.... or the same size at the Executor's smallest official measurement.
I wouldn't be particularly surprised if we did see a new SSD or a 'galaxy gun' style weapon over another battlestation. So, a list of SSD type ships in the Galactic Civil War era (excluding Clone Wars types).
Assertor-class: 15km
Bellator-class :7.2km,
Pro: it's pretty prototypical and slightly smaller than the larger sized Executor estimates.
Con: it's not much smaller, it's got the same command tower problem it not worse as there's little in the way to obscure it (and at a reasonable scale, the tower might not even show up), and it's far-far thicker than the Executor.
Eclipse-class: 17.5km
Pro: It's unique looking and might actually be possible.
Con: It wouldn't be any smaller than the Raider in physical size, but might have to be longer. That's a lot of material. That said, it's no Executor in shape, and while I love its profile, I'm not sure how well the humpback would be received.
Executor-class: 8-19km.
Pro: it's big given its shape, but its bridge isn't actually superimposed from an ISD. It could be any size and work perfectly well.
Con: It's got really low detail and it's a sort of strange shape that looks more at home in Firestorm Armada, but it could still work (might be one of the best candidates)
Mandator-class : >8 Km
Pro: it's in the movies and thus recognizable and iconic, there's not much competition out there, and its got at least decent structuring from what I saw when it comes to plastic tooling. There's also a prototype confirmed at 12km.
Con: the bridge size, people's preconception on how big it should be (whether it's 16” or 36”, there's going to be complaints), unsure how much detail they can put in to the 'city-spine' and still make it look reasonably detailed.
Praetor II-class: 4.4-8km
Pro: no one's ever seen it depicted.
Con: no one's ever seen it depicted AND it's part of a private fleet from the late Clone War era.
Sovereign-class: ?km small scale version of the Eclipse.
Pro: workable enough size. There's no real 'bridge' or prominant features to scale.
Con: There's no prominent features at all, really. It certainly doesn't look like an SSD or anything particularly special. Its got a lot of flat surfaces and some massive looking subwoofers at the back of the 'tower' spine.
Pro: no one's seen it, it's described as being smaller and reasonable to mass-produce.
Vengeance-class: 19km
Con: only 4 built compared to the 'dozens of command ships' that describe Executor-like vessels, and all built by a splinter faction, Warlord Zsinj in the EU.
Pro: ... well, you can see the bridge I guess.
Con: Executor but more spindly which makes it harder to scale, only 3 built, tiny slender wings,
There are other classes, but then fall into the 'battlecruiser' territory between 2-8km long. We can always talk about those but they're not really SSD-like.
Big "Like" here.