They could add a Weapon class that deals specifically with Oriental Swords and call it Iaidō (居合道?).
They would use Katanas and Great Katanas and they would would teach Ninja, Monk, Samurai, and Dragoon skills.
Then once you had enough of the skills learned from using Iaidō you can become more proficent with those as jobs. But play with those jobs on any weapon afterwards.
For Ninja, I think one of the things they could do for it, is the skills it has that are basically its version of another already known Elemental Spell (Katon = Fire etc.) Make it so when Ninja is your Job and those spells are equipped they transform. So equipping Fire while on Ninja would turn it into Katon. etc.