So what are some of the ways you implement "jobs" in FF games where they don't exist?

[Laddy]

I pretty much only did that in FFVII.

Cloud-Green Mage (More of a fighter, but used status spells.)
Aeris-Black Mage
Tifa-Monk
Barret-Warrior
Red XIII-Red Mage
Cid-Dragoon
Cait Sith-Blue Mage
Vincent-White Mage/Summoner
Yuffie-Thief

(Yeah, pretty dumb, but I beat the game like that, was very strict, for example, only Vincent summoned, Red XIII never mastered spell types.)

Overall, the class had to fit personality.