Arithmetician has always seemed odd to me because if it were to be in the game, then 1) it would have to find REALLY good differentiation from Arcanist, and 2) it would have to be able to work without percent-based skills since judging off of the 3.0 adjustment to Lustrate for Scholars, such skills just wouldn't fly.
Beastmaster will probably happen in the very distant future once pet controls can finally be fixed.
Blue Mage.....*points to sig below*. The short version is that it could be done, but not in any way that the XI diehards would approve of.
Cannoneer & Chemist individually seem too bland to me, although combining the two would be a lot more interesting.
Chocobo Knight looks cool at first until you realize that Roegadyns are a thing and then having to visualize a big fat chocobo with a big fat Roegadyn on it that could potentially be bigger than a lot of enemy hitboxes.
Corsair feels like a combination of Astrologian and Machinist to create a masochist's dream job.
Dancer is going to happen eventually, and I'm almost positive it's going to upset some group of people when it's announced.
Geomancer would only be cool when we get to see that what would be the playable version would be a million times cooler than anything seen in that Astrologian storyline.
Gunner is already a thing. It's called "Machinist". Moving on....
Hunter and any other bow-type job, unless they're rocking at least one crossbow, probably won't see the light of day so long as Bard is still a thing.
Juggler would be cool, which reminds me that I should update this concept.
Mystic could potentially be slated for 5.0 because of Yoshi's original intention of wanting an Eastern-themed caster class.
Mystic Knight would probably be the closest thing we'd get to a Garlean job. Lots of potential for it, but not really something I personally find interesting.
Necromancer has a whole other thread about it, and is currently identified in the game as just a Black Mage on steroids.
Orator is one of those jobs that could only exist in FFT. It's kinda like making Alphinaud his own job, and nobody wants that.
Psychic I wouldn't mind just to see how the lore for it would go.
Puppetmaster, like Beastmaster, also falls into that category of "not until pet controls get fixed". I'd also love to see something that doesn't look like the XI version.
Sage, as it usually is in FF games, is likely going to be too powerful mechanically, so it's definitely something that'd have to undergo extreme changes for it to happen.
Time Mage is another job that would likely wind up very different not only due to how many abilities associated with Time Mage belong to Astrologian, but also because Time Mage in the HW Astrologian seems to be just an empowered Astrologian.
Viking would be nice, but given how much devs aim for some level of accuracy for their historical inspirations, they likely wouldn't use hammers. Maybe a halfspear and shield or a one-handed axe and shield because all the other weapons that Vikings would have actually been historically known to use are already taken.
My vote went to Green Mage with Morpher being a close second since that's the closest we'd get to bona fide DoM tanks.