Silver,
The whole point of implementing the Job System was to bring Traditional FF Nostalgia and Role Specialization to the Armoury System.
Weapon Classes (Armoury System) Are weapons. Musketeer is a GUN user. Fencer is a Fencing Sword User. they are not Jobs.
Jobs are Role Specializations based on the Traditional FF Jobs. Ranger is a Ranged Specialization. Thief is a DD/Crowd Control Specialization. Paladin is a Tank Specialization. They are not Weapon Classes.