EE's system was based around XI's job/subjob change system, the one thing that differentiated it was you could:

Level class 1 - Learn a class trait
Level class 2 - Learn a class trait
Level class 3 and equip trait from class 1 and 2 if you so chose, which was up to 3 I think? Might be different now since I haven't played it since summerish.

All that's really known about the new job system is some will have dual class requirements, like PLD requires Marauder and Gladiator leveled to unlock, but the exp gained as PLD will go towards Gladiator and vice versa, since he mentioned 'job stones' of some type which means it may be the same way as Sentinel is an 'add-on' to Gladiator, Conjurer and Thaumaturge.