so it's like, you'd need to either fill it out with OCs beyond a base roster, or make it some extracanonical thing like the persona Q games, along with reconciling the stuff between Strikers and Royal (if they can even use Wolf and Sophia, i have no clue lol)
at which point, it doesn't really need to be Persona 5 Arena anymore, and you can just fill the roster out with characters across the series
i unno, it's just a weird situation to me.
In a way it might be like the Persona 1/2 -> 3/4 situation all over again. Persona 5 sold much better than the previous ones, so maybe they think that bringing back older characters from games that sold worse would alienate the Persona 5 audience. I think that's a bad attitude, but at this point it seems to be happening. It probably doesn't help that their one attempt at a crossover with all those games so far, Persona Q2, did pretty badly compared to its predecessor (although the 3ds dying early probably played a big role there).