I don't think this would really be worth the hassle compared to just making new jobs.

SE have been trying to distance SMN and SCH adn diverge them more over the expansions I doubt they want to slap on a bunch of similar scenarios to these.

And some of the base classes I feel don't really have enough to go on anyway. THM and CNJ are basically black mage and white mage lite anyway. Pugilist is very similar to monk as is, just with less of a focus on form and more of a MMA feel it seems from the way the SB monk quests compare them having Pugilists being better able to fight those trained specifically to counter monks. Lancer and archer I don't even remember having much theming or interesting lore outside of 'we use lances/bows.'

The only one I'd personally probably be interested in seeing devloped would be rogues, but that's mostly just because I find the Rogues as a group more interesting than Oboro and his ninja buddies.