To be frank, classes are pretty pointless in the grand scheme of things. As soon as you equip the job crystal you never look back as to be fair there is no real reason to. The amount of cross class skills are severyly limited making the choice of what is usefull pretty mandatory.

But they can still cross job abilities, maybe with the removal of the class system they can expand on that even more allowing for more variety in choice. Also they could easily add prerequisites to unlock jobs by making it similar where you need xx level in one job and yy level in a second job to unlock the new one. As a theoretical example, 15 PLD and 30 WAR to unlock DRK.