I can't say I am thrilled with the new system but also not thrilled with the FFXI version either. Maybe an implementation of both systems is in order. Bear with me here this might be a bit lengthy.
Assuming this:
Class = Skill set
Job = Role
Keep the Classes as they are including the current max level. Upon achievement of certain class levels you can unlock an "advanced" class. These advance classes would be the more traditional named jobs. The hook to this would be that these advanced jobs would require multiple classes to unlock.
Example:
Red Mage would be an advanced job. To unlock the quest necessary to become a Red Mage you might have to achieve Conjurer 30 and Thaumaturge 30 and complete the individual class quests associated with them. You might even want to throw in Gladiator 20 as a requirement as well.
In short you would need to train your "Classes" (skill sets) before you could perform your main "Job" (role).
When you graduated into your new role you could still use any and all abilities that you could from those classes needed to gain access to the new job. However you would be limited to selecting from those classes when setting up your skill bars for your job. The new job would also have its own set of specialized skills only available to that specific job. You would then start leveling your job and getting the new abilities that it offers and still have the option of reverting to the individual classes to train them further (possibly for gaining access to other jobs or gaining access to other abilities that may help the job your are working on).
Using this style of system would also allow the introduction of job specific abilities such as 2-hour abilities. This would also allow SE to implement more classes and jobs to the game based simply on the requirements necessary to get a job you may want to try and implement more questing content into the game. In addition you would also gain the ability to use multiple weapons which would only be restricted to the classes needed to gain access to a job. For Red Mage you could use Sword, Shield, Staff and Wands to go one step further with the example above.
One last note I would like to make about this style of doing things would be that I am seeing a lot of posts about how people are upset about how easy the game can be at times and how it seems to be so "solo" oriented. Using this system would allow for both solo and party based content. The quests you would unlock for your classes would be primarily solo content while job related quests would allow for a more difficult curve and have more of a requirement for party play.
Just some thoughts on how to have the best of both worlds...Sorry for the wall of text.
Mort
PS. You could also work other classes like crafting and gathering into the requirements. (ie. The Alchemist job would require Alchemy to a certain level as an obvious example.)