So while the producer loves to tease us about a job system in the works I'd like to throw my 2 cents in on this one with a few thoughts...

a) Jobs should be flavorful to the FF universe
b) Jobs shouldn't phase out the Armory system- the two should be intertwined
c) As in any game, Job balance is CRUCIAL

So here are my thoughts on how the Job system should work...

-Jobs should have prerequisite Disciplines (IE Monks require both Pugilist and Thaumaturge training, Geomancers require Botanist and Conjurer training).
-Some jobs should meet only one, very high prerequisite (Summoners should probably be R50 Conjurers)
-Jobs should NOT increase the PLv or R# cap, but be stand-alone disciplines which define the PC better by combining armory skills and Job skills.
-Jobs should be a MEANINGFUL decision for the player- not something to swap in between raids (perhaps even a form of permanence)
-Jobs probably shouldn't be added with expansions, but instead be solid character archetypes who (like disciplines) unlock special skills in expansions

Just my 2c worth... Jobs I would like to see in FFXIV
Red Mage
Blue Mage
Summoner
Moogle Knight
Chocobo Knight
Dragoon
Thief
Soldier
Fighter
Geomancer
Sorcerer
Monk
Hunter
Trapper/Ranger
Scholar
Berserker/Viking
Devout
Magus

(just about anything from FFIII I suppose accept...)

Jobs I would not like to see...
Dark Knight
Ninja
Samurai
Knight

Why? Flavorfully they kind of retract from the colorfulness of FF games and are usually an advanced form or lower form of another job