I'd say right people, wrong slots:
That's the thing, it really depends on where you got into the series. If your first game was SoulCalibur II, then your reaction to Li Long, Hwang, and Arthur in SoulCalibur III was like, who are these random people? Whereas people who had played SoulBlade and SoulCalibur before it were happy to see some old faces return. Arthur less than the other two, given his circumstance, but I'm sure some people were still appreciative all the same. Those same people are likely to prefer Seong Mi-na's return, because they're still low-key (or not) distasteful of Kilik for essentially stealing her spot by taking her style and running with it, and being critical to the plot, while she just kind of chases idiots around for a living.
But that's why I'm happy with the prospect that Hwang may actually make a return here, since this is his territory, and it can be seen as somewhat a compromise, where Li Long sadly has zero chance, Yun-seong is also quite meaningless to the plot, while Maxi is quite important, so Hwang can take his spot back and not only flesh out his character more, but give Mi-na a second chance at life too. While it's possible Yun-seong could also do this, he abandoned Mi-na in SoulCalibur III to pair up with Talim instead, which led Mi-na to chase Talim in SoulCalibur IV... it's just so backwards.
But if we can only have so many characters, I feel like what you listed is the best compromise to have the old and new with styles and all included. Setsuka and Hilde can come via DLC, so we'll have their styles too. Cassandra maybe too, though I think she's got a chance of being on the main roster too, instead of "New" on your picks, since
@Vergeben highlighted that Grøh would be a boss character, I've just got this mental image that he's going to be like Night Terror, some overpowered monster who would be too much to be playable.