There have been a few threads like this, and some even with posts detailing what people would like per job. And just to contribute, was made really quick so bear with it =p

Archer -> Ranger (because what else?). Archer/Thief. DPS.
Pugilist -> Dancer. Though I'd prefer Dancer to be off of thief class (for dual dagger like in FFXI). DPS/Support along the lines of Bard (dances to work like songs, different effects). Pugilist/Conjurer.
Gladiator -> Red Mage. Soulstone removes enmity multiplier from attacks. GLD/THM (CNJ for other cross class). Would prefer if RDM came of a new class, say Fencer.
Marauder -> Dark Knight. Soulstone removes enmity multiplier from attacks. MRD/THM (LNC or PGL for other cross class)
Lancer -> Samurai (Yeah cry foul, Samurai used polearms too. Not just Katanas). LNC/GLD or MRD. Tank
Conjurer -> Geomancer (Makes sense with the lore around CNJ in the class quests). Healer (or DPS if cures are changed to something else)
Thaumaturge -> ???