I was thinking maybe Red Mage could be a tank caster class/job. I guess if it starts from start it would be something like Spell Fencer, or maybe just Fencer, then as a job promotion it becomes Red Mage. The idea is that it's a caster job that operates as a tank. I haven't thought out every little ability or anything but the basic are as follows. The class/job first of all uses intelligence as its primary stat like all dps casters do, however it has a unique 1st level ability that works similar to Cleric Stance in away but rather than swapping Mind and Intelligence it swaps Intelligence and Vitality, thus increasing your HP so as to be more tougher. They would gain spells that they could use to attack aoe or individuals that build enmity, this spells would have really low cast times, we are talking some of the lowest in the game with at least one basic one that is instant cast, however the trade off is mp cost, and lower damage when special stance mentioned above is active.