There is no fucking way we're not getting P3 characters. And Marie... I can't imagine that would ever happen unless Atlus were specifically to push for it, which they might I guess...
There's no way they're ignoring the Izanami connection.
So is making a crossover with a PR manager that says that characters in said crossover don't matter, and that they're just "functions."
... *sigh*
Okay.
Adachi or Teddie would make as much sense. Or a surprise character not previously featured, though I would probably be surprised if that were the case.
I almost asked if it was possible that it was a new character but then I realized how stupid that'd sound since pretty much every notable P4 charcter is playable and there's no one else to add.
Dojima with Nanako as a persona assist.
I mean they could do some p5 stuff or they could do like literally any character, obviously dojima or nanako are possible, but really they could add any persona character.
You forget P3 characters were present, and Blue Jesus has yet to make a fighting appearance. I doubt this game is canon to Persona, so why not?
Mitsuo?
If they can make Persona Q canon (even with a memory wipe justification for not remembering its events), they can probably make Cross Tag Battle canon.
Inb4 it's the crutch of RWBY Season 5's plot.