The best solution is really just to leave the existing classes in the game, even if they're just some archaic holdover at this point. There's really no value to reworking all of the pre-30 story stuff, to say nothing of the inevitable fiasco of trying to divorce SMN and SCH, just to tidy things up. Since they're obviously not interested in expanding on the class system, whatever, and just keep making new jobs with no base class.