The game has a take on Red Mage, complete with dualcast, except dualcast will only cast Red-only spells, which are all tuned to be half the potency of the core White/Black counterparts anyway so in the end you're paying 2.5x the MP for the same effect.
Though I guess you still get the flexibility of having an effective dual-role caster then. No AoE though, so you can't be a main heal without also slotting White.
It's like they loved Final Fantasy V but were afraid of the game-breaking potential.