Quote Originally Posted by Grey_Cain View Post
2.) Blue Mage XI gets a new blank slot instead of an ability that it can fill with one of the monster abilities that it's learned. Abilities are learned permanently, but only a limited number can be set. As a Class, this version can set up to 17 abilities. As a Job, it can only set 5 at a time.
Given the way this game is set up, this seems the most likely. The quested abilities might be something more like unlocking new tiers of spells to learn. Then use a modified version of the cross-class tab, with the icons being for ability tiers instead of other classes.