Do you think a Blue Mage is feasible? I Mean honestly... The Original GW is like the only MMO To have a mechanic similar to a Blue Mage. "Capturing" Abilities and copying them is one of the iconic features of a Blue mage. But Simply unlocking them through story quests would leave it feeling like other classes. You would almost Have to leave their ability gain to Class quests in order to keep it balanced and to be frank, due to the lack of variety of "Builds" in FF there is no way you could just allow the Blue Mage to "Capture" and "Copy" Skills of enemies. TBH It would take away from the magic of a Blue Mage and leave it feeling like any other spell caster.