There are some people who theorize that the second new job in the upcoming expansion will be blue mage, actually, so this idea might work even better than you think. But even if that doesn't turn out to be the case (and I'm pretty sure we're going to find out for certain during the EU Fan Fest in February), I still wouldn't consider it lore-breaking to play a character who learns new magical skills via observation like a blue mage. If your mage character is particularly clever and willing to get hit with some unpleasant magic in the name of science, I see no reason why they couldn't pull it off. 
Michaux Vidal - Oyuna Qestir - Tatsu Kaisuri
Arnvi Sunblade - Noriyasu Kuroda - Lucien Lemaire - Bren'li Arhys
(See Tumblr for Character Profiles)
