As neat as it'd be, and as I've said before, if jobs were limited to gender (or worse yet, race), it'd pretty much be a nail in the coffin known as "balance" unless all of the jobs were more or less exactly the same. I mean god knows the game'd be much worse off if it went with a theme like "DRK and /DRK = Elvaan only, SMN and /SMN = Taru only, NIN and /NIN = Mithra only, WAR and /WAR = Hume only, SAM and /SAM = Galka only"
Neat concept, but would terribly break stuff unless every job was of exact equal useful/uselessness. And we all know how good SE is in that department. =/