I'm not sure if maybe there is some reason, like maybe it could be exploited somehow, but I would really love to be able to go back through all of the story on different jobs. I experienced it as a Paladin, but what would it be like as something else? If this is at all possible, I would so appreciate making this happen!
If there was exp then everyone would find how to get exp the fastest via newgame + and ignore all the other content. That would make it much harder for people doing the story to make progress since people wouldn't run the dungeons anymore.
Bots.
they exist, and that's why it'll never happen.
The big rewards are there to keep you playing on the first job, to make it move at a good pace to keep you motivated.
The latter jobs get the armory bonus to make up for that and make it less hard to level them, but it'll never be quite as much as the first time.
My pet peeve is that you can't NG+ and start in a different town and see what THAT would be like, and you can't get the achievements for those towns.