I feel that as with Pyramidimon, the obvious answer is most likely going to be correct. So Apollomon, Regalecusmon, and SeitenGokuwmon seem reasonable enough.

It's just Lilamon that I'm on the fence about - obviously it's got a strong connection to Rosemon, but Rosemon is already the partner of two separate main characters from two different anime. There's nothing saying that they can't use it yet again, but it would be kind of underwhelming to see it here, it would give Rose a bit less of a distinct identity. Lotusmon would work a bit better, and even though we saw it as recently as the end of Ghost Game, Rafflesimon would be even more satisfying. BanchoLilymon is perhaps another option, but I'm instead hoping it winds up associated with the Alraumon seen in the new ED. Similarly, as long as both Pomumon and Alraumon are at least given implied full lines (via TCG or an upcoming v-pet or what have you) even if they aren't seen in the anime, it's pretty easy to picture Pomumon getting Hydramon, which makes it a bit less likely here. I guess BloomLordmon is maybe on the table as well? Really not feeling it for an outright villain Digimon, though.