Unfortunately, as much as I would love to see Chemist as a DoW/DoM or Job, because there is already Alchemist as a DotH, unless SE gave it a different name to avoid player confusion, I don't see Chemist being added to the game as a DoW/DoM or Job, for the above reason.

Also, the reason why Chemist could use guns in FF Tactics I presume was because they would use their chemistry skills to make the gunpowder that powers them (the guns they used were old muzzle-loading flintlocks and muskets) - Chemist also didn't lead to a Musketeer in FFT - the only other Job in the game that could use guns was Mediator, which, ironically was very much like SCH in a way.