Or the simpler solution is to just slightly change the lore to accommodate. Much easier.

Mechanically "Marauder" would be the same job as Warrior. However, in the quests/lore, it would be more of a right of passage sort of thing. Fledgling Warriors are referred to as Marauders, and once you reach level 30, you have proven yourself to be a full-fledged Warrior.

And I don't think it needs to be mentioned that they are nowhere near willing to create 9 new full jobs. Sure, roughly 1/3rd of each are already "done", but when you consider they didn't even want to do/couldn't do 3 jobs in 3 years, it would take them a decade to fill out 31-80/90/100 worth of skill lists. Also, that would create a HUGE bloat of jobs.

I like your intention, but it's not anywhere near realistic. Thought experiments are nice, but they're only really useful when there's at least a vague chance of them to possibly occur.