I would love if they'd put in a Maximum Impact team to carry on its story in the main series as a side thing that's going on. Kind of like the Hizoku clan stuff from NESTS saga or the Dragon Spirit thing that I think is still going on with Kensou. Alba Meira, Luise Meyrink, and Xiao Lon would be my picks for that team. If they wanted to use any more characters from that series they could probably fit Mignon with the Psycho Soldiers if they're willing to bench Chin and uhh Chae Lim can hang out on Kim's team if they want to differentiate the two of them even more.
They'd need to either make Addes members mid-bosses or the boss and I don't see them doing that. So an Addes team would be alright with me. Duke, Jivatma, and for a 3rd character someone new, a brainwashed Soiree, or Nanase. Judeim would be cool as a mid-boss but then they'd have to make Alba disappear from your team in story mode. Would be worth it though.
I fully expect them to just do something completely different and unexpected with the story since apparently everyone that was dead is magically alive in this new timeline. As long as the art direction is better than XIV's was and the gameplay doesn't throw away all the fun new mechanics then I'll be there day 1.
I mean look at these people. They're fabulous and deserve another shot in the HD era.