I agree with Pence, this is unnecessarily complicating things for complication's sake. Classes upgrading to Jobs is something that SE kind of considers obsolete anyway (classes were an old relic of the original version of FFXIV which Yoshi changed to upgrade to Jobs, which was carried into ARR, and it's a 1.0 Legacy he's trying to away from, the 'extra Jobs' which have no base class being introduced in HW and now here in SB as well are an example of this), so a 'third' upgrade will not add anything to the game other than making things even more complicated I'm afraid.