This is a fascinating discussion of alternate possibilities, but hasn't it already been confirmed that Rogue will be a class and Ninja a job? Classes start at 1. Jobs start at 30. If SE wants to add a third tier that starts at 50, it would be something other than a class or job. A specialty, perhaps, or a vocation, a calling, a trade (perhaps that last one works better for an advanced crafting class). Anyway, there are plenty of other terms they could find that don't already have a different meaning within the game.