Well, I could see bluemage as a tank, since its gimmick is being hit by enemies. So make jobquests in a way that a player tracks and provokes a monster to get hit and learn its skill, and give a nice emphasis on parry and counter, kind of like what DRK currently has going with TBN. (Also, wouldnt it would be cool to be able to glamour 2 different scimitars?)
Alternatively, judge Gabranth from FFXII has cool weapons and, in dissidia, a cool toolkit, that I could see working on FF. Combine the weapons in tankstance, and seperate them in DPS stance, and then dance away.
