I think of them as "Advanced Jobs" I wonder if it will strictly be a quest requirement to unlock or will you need to have X level Class or Job to unlock? I suspect it will be a "Go on a quest to find the Buster Blade" sort of deal, then that weapon will unlock the Job. Since these are using new weapons previously unavailable in the Eorzea I'm sure we will start at level 1 to learn to use it.

I'm still quite hopeful for an actual titled "Advanced" Job to come at some point in time where you will need more than two class/job's to unlock it (Red Mage = GLD + WHM + BLM all level 50(?)) Also still hoping for Jobs for the DoH and DoL classes that are more focused in their craft.