Red Mage is pretty much a hybrid everything, Kaurie. White and black magic, ranged and melee, physical and magic.
Personally I would add another twists to it. Dunno what you guys say but I would update the traiditional rapier into a gun rapier. Ala Mhigo was famous for its magitech even before the Garleans came, and having playable benefits of Garleans rule could make the central conflict more effective. Is the occupation really that bad?

The gun part could help channel some of the offensive black magic spells.

As for role, it could pretty much fit any role.

TANK: IRL rapiers come with hand guards and have been traditionally wielded with off hand daggers and shields for defense. Also RM could use white magic for damage mitigation beside parrying.
DPS: It has a sword designed for stabbing, and a bunch of black magic spells. I don't think this needs more explanation. It has damage written all over it.
HEALER: might cause controversy if this ends up being real, but with white magic spells it could happen. Like and anti bard. The two support jobs turn into ranged dps and melee healer.

As a central mechanic I could see red mage balancing white and black magic. Maybe if you use too much of one type, a debuff locks you out of the other. Or perhaps you could build up aether inside you with melee combat and use that to launch powerful spells. (Looking at you, dear Alisaie)