I..what?
I think you made far too many assumptions here.
There are certainly a plethora of class/jobs that could fit the ranged/debuff position.(I mean, if we wanna look back at FFXI*gasp*, then a Musketeer/Corsair would fit nearly perfectly) But even that is just a shot in the dark guess.

I'm sure like others have stated, that Red Mage is most likely to come with the Fencer class.