I'm hoping they go with the Mystic Knight side of the class.

Give it En-Fire, En-Lightning and En-Ice, which would be an MP draining toggle, these spells would turn 100% of their physical damage, so all auto-attacks, weapon skills, and offensive abilities would turn into magical damage of the appropriate element. Each en-spell would also offer different debuffs on the enemy, like en-spell would lower the enemies resistance to fire and lower the enemies attack, while en-ice would lower the enemies resistance to ice and lower the enemies evasion, possibly also grant slow.

They would also get Elemental Blast, that would change element based on what en-spell they were currently using, which would be a PBAOE which would vary based on proximity to the target. They would be able to chain elemental blast off of certain weapon skills.

They would also have "Cure".

Elemental wall would be another one of their abilities, which is a protect like spell, based on the currently used en-spell, that would offer a little big of protection like protect, but not magical damage in general, just resistance to the respective element, it would also be a toggle, draining MP as it's active.

Maybe a self refresh.

Something like that would be fun. It'll be more like the Red Mage from FF1 and less like the refresh/cure bitch with a sword from FFXI