Kasumi can have different movement animations from Joker like Dark Samus; her movements would be more graceful to reflect her ballerina background. I think she's more likely because aside from having leftover data in the game, she looks the most like Joker visually. She has the red gloves, the black clothing, the longcoat and the pointy shoes, and the mask. She can also have the same school uniform as an alt costume. Unlike Yosuke and Yu, she wields one melee weapon and one gun like Joker, and the Rebellion gauge wouldn't make much sense for them either. And based off of the animations we've seen of her fighting style, it mirrors Joker's, too. She might not have a grappling hook, but they can feasibly give her a ballerina ribbon instead. And she can be used to promote P5 Scramble for Switch, the same way Atlus is using her to promote P5R.
Visual comparison:
Fighting style comparison: