I know plenty of people who play on controller just fine, including two of the best Scholars I know. I'm sure BLM would be easy enough considering Scholar is a more complex class.

Have you considered an MMO mouse? The buttons are all very close and the majority of them are where your thumb would naturally rest on a normal mouse, so I think it could fit your situation. You could hotkey many abilities to them, as well as enemy targeting so you don't have to use tab.