Like Joker, Makoto doesn't actually have an attack type that translates well if she were to become a Gym Leader. Her Persona gives her the ability to use Nuclear moves, and that's not at all helpful for this list.
Fortunately, I can think of a type just by looking at her. It's steel. It has to be Steel-type because Makoto's Persona is a literal motorcycle, she fights with spiked brass knuckles, and her mask is basically just a metal plate.
She's also a lot tougher than she initially appears to be, with a no-nonsense attitude. These would be her Pokemon: