As I was discussing with one of my FC mates, I'd love to see something similar to the Blue Mage as well ... but a bit different than what people are used to/thinking about.
I'd love to see it as Relm in FFVI, utilizing paintings to copy monster abilities. Throughout the Job Quests, you could be given new types of paints as well as monsters to make portraits of during battle. Perhaps switch between paint colours similar to stances or the like. For instance, with a Red paint coat you could mimic attacks of Red Dragons, Bombs, etc. But with Blue, you could do things like Sahagin or some of the many aquatic-themed monsters. Perhaps even past level 60 you can cross-paint, giving you the ability to paint portraits of monsters with multiple colour schemes. These would give you skills and buffs like Aqua Breath for a cone shaped spell in front of you, or an explosion attack in an AoE around you that takes either a portion of your HP or gives you Vulnerability up for a short time.
I think it'd be an awesome idea. I'd also love to weild a massive paint brush with magic-imbued paint during battle to do close range magic damage with auto attacks.