Well, summon is technically a ACN thing, so as a CNJ, there could be no fairy.

But looking at how minor of a role jobs play (way less than subjobs played in XI), I seriously doubt there's going to be issues with balancing. Worst case (and best) scenario, classes simply perform best with the job they were meant for.

In XI, the time it took to bring a class to 75 was immense (pre-abyssea, compared to what it takes nowadays), and during leveling most of the innovation occurred and was accepted. It doesn't take near as long to bring a class to max level in XIV. So a change like this would be useless.

That doesn't mean I don't think it would be fun. But yeah, I agree now, it's not realistic to suggest this.