Going the traditionally route I'd love to play as my summoner again, just like everybody else.

But thinking outside the box:

Dragoon/Wyvern Rider- You can fight side by side or choose to ride on, the Dragon of your elemental choosing. ( The Riding on would be similar to that of the Eidolons in FFXIII)
Beast Master/ Blue Mage/ Shapeshifter - instead of Charming or learning the Mobs moves you're able to become a mob.
Dark Sage/ Necromancer- (This could very well be what Arcanist/Mystic is suppose to be)
Light Sage/Cleric- (This could very well be what Arcanist/Mystic is suppose to be)