Final Fantasy I had job upgrades even. White Mage - White Wizard, Black Mage - Black Wizard, Red Mage - Red Wizard, Black Belt - Master, Thief - Ninja, Fighter - Knight. I know this can't change exactly like this, as thief and ninja are seperate jobs now, but this is pretty much how it happened. They introduced higher stats, ninja gained use of black magic like drk and knight gained use of white magic like pld. Also, the mages gained access to more spells themselves upon upgrading.