As for all of the talk in this thread on how they'd implement BLU without a Learning ability, they could pretty easily do it.. We just probably wouldn't like it.
Learning could be classified as a General ability so everyone has access to it, even without unlocking BLU. Pop the skill for a temp buff, making it so that when the monster dies, there's a chance of some kind of monster essence loot--mechanically, this would be the same as Rogue's Mug ability. Each job quest to advance BLU would require you to turn in a set of essences, especially to even unlock the job, guaranteeing a functional set of basic abilities.
If they wanted to go an extra step to make sure you can't have an underskilled BLU in harder content, they could probably make each job quest a level cap unlock as well.
What I wouldn't like is how, given a list of
recurring blue magic in the series, some of these abilities would require farming bosses in dungeons and raids. And the devs have been trying hard to keep older content relevant...