"New game plus - quests will have no rewards..."

[Iscah]

No, you're misinterpreting what I said. If you have a job who hasn't done the MSQs, you get exp. Obviously, that means that you get exp from each MSQ one time. One. That's once. Not Twice. Once. Per job.

No exploit. There is no exploit that way.

Get it?

Except that involves a separate system to track which job "has done the MSQ" - in a game where you can switch jobs freely and might have equipped five within the course of a single quest.