What do you think of the Baram/Kefka theory?

Right. The big thing is, when you go to Vector for the first time, if you go up to the pub, there's a Returner sympathizer, who tells you a secret. He says Kefka used to be just a normal soldier, until he underwent the Magi-Knight experiment. He explains that something inside Kefka snapped that day, and he lost his sanity, basically.