I agree with this assessment.
Making Scholar into a classless job should be easy enough--it is already far removed from Arcanist, with its own action set and quest flags.
As for keeping classes out of duties, just require a job for any duty over 35. The DF understands how to do this, as evidenced by PvP. Extend it to the rest of the DF beginning at 35. Aurida's suggestion to make gear equippable only by jobs is also relevant; if combat classes can't equip any gear over 35 or 45, then they also won't be able to queue for anything with a minimum IL.