Samurai: As mentioned before in KillerClown's post, Add the Saya's the The Samurai's arsonal. Just for stat boosts, maybe even a "shield" skill/block type thing tied into the parry skill.
Dark Knight: Absorb-TP Spell, Level 60+ ( I know Sam may be getting something like this, but man... it would make DRK so rediculously useful in HNM fights for once....)
Red Mage: Contagion Transfer(In the game already) a 5 or 10 min ability, like monks' Chakra, instead of 'healing', you transfer all your status effects to the mob you are fighting. For instance, if you are fighting a Skeleton, and you get paralyzed, Choked, and Blinded, you hit Contagion Transfer, you are healed up and the skeleton has Para, Blind and Choke now.(+/- resists)
Alt 2hr?
A series of Questable 2 hours that can be added to the jobs:
Monk: Grapple, Immoblizes the enemy from doing any action for 30 seconds (Stun on crack)
Thief: Soulsteal, small percent chance at immediately killing a mob.
Black Mage: Ultima, Charges HP/MP to 100% then proceeds to unlease both in a tremendous flow of energy leaving the Mage with 1 MP/HP. MASSIVE Enmity.
Dark Knight: Zombie, you are uncontrolable, and invincible for 1 min, you attack anything around you(melee only). Party members and Foes alike. You basically give yourself to death, and become a fomor till your minute is up.
Blue Mage: Rage, you assume the role of the foe you are fighting(and a all it's moves) for 1 min.
etc...