Hmmm Part of me wants to say he'd use Dark type Pokémon. And the player has to defeat him in a Pokémon battle to stop him from his plans in the pokemon world.
Though on the other hand, (This was on total accident and I didn't realize it until just now) The three poke balls he has might as well be TAV. They after all were kinda his pawns in his plans. He used all of them in his own way. I'm trying to figure out how Ven and Vanitas work though.