I love how Yen Sid isn't even an option LOL. Well, I'd probably be self-trained if anything, but if I had to choose... Maybe Mickey. I really like the Light-based attacks he and Minnie have in their repertoire, and I'd wanna be able to do stuff like that too. Plus Mickey should be the strongest out of all of the Masters on the Light side. Before ReMind, I would've given it to either Aqua or Riku, but that little mouse had one of the greatest scenes in all of the franchise up to this point and I gotta give respect where it's due. So I'm going with King Michael Theodore Mouse.