Red Mage, confirmed!
I doubt it will be Red Mage. Red Mage will be Fencer, not Musketeer.
The problem with this theory is that rogue/ninja will dual wield two of the same type of weapon in main/off hand and it makes sense to pair them. What you're describing is not.
In 1.0 when they added auto-attack it was speculated that a dagger would be added to archer for close up attacks. SE said at the time that this would not be the case because the armory system is based on the weapon that's equipped. Allowing them to equip both a dagger and a bow would in fact not fit within the armory system and no close up weapon was added. That fact, as stupid as it seems, is the reason a bard/archer punches when it is up close for its auto-attack.
While I hope your speculation is true, based on what they did with archer to solve the ranged/up-close attack does not lend to it being the case (barring a change to the armory system).
Yea, I'm willing to bet that it will be Chemist also in Final Fantasy Tactics Chemist were able to use guns again back to FFX-2 where Alchemist was basically a white mage with a gun.. Plus if they are digging for roots of the FFseries Chemist would be it.. I also feel that chemist would be buff heavy class/job which specialize in Aoes.. I can already see its cast animation of chemist going into its unique bag and tossing potions.. lol.. so neat..
so here it is again I just love this FFT style pic.. http://dlgames.square-enix.com/fft/img/jobs/c02_en.png
I want Chemist SO BAD. So, so so bad.
FFXI Red Mage was not what a Red Mage should have been, in my opinion. They were support instead of being a physical / magical hybrid.
I want it too, and think it would be cool, but it would have to be reagent based for me to like it. Like, they actually must have the items to use them on other people. Otherwise it would be unfaithful, in my opinion.
I realize this could be problematic for inventory space so perhaps we/or just Chemist could have a separate inventory for potions? I don't know.