I think I'd be either a Fighter or Red Mage.
A Fighter is a tank, who hits hard and can take a real beating. Of course I'd have to act as a meat sheild for my allies, but high defense and HP means I can do that for a long time, so long as I've got a White Mage backing me up.
Then again, a Red Mage makes an adequete attacker, and in all ways is versitile. I can see where being able to cast both white and black magic would come in handy, as well. The only problem I see with RM is that he is too versitile. He is okay at everything, but not really great at anything. A jack of all trades, yet master of none.
I'd much rather be a Fighter, upon further deliberation. And after class change, I can cast low level white magic. And that, to me, is very, very good.