Thm really throws a wrench into the job system and will be the hardest to make sense of the decisions.
Blm and smn are classically elemental in nature.
Whm is counter cultural to thaumaturgy.
Red Mage- plausible. Wrong weapon though, hard to define a real party role.
Time Mage- plausible, potentially game breaking to give thm hastes and meteor.
Blue Mage-plausible
Dark knight- hard to argue an entire change in discipline.

I'm going to guess time Mage. Emphasis on boosting performance of party members.