They are not making any major changes to the armoury system they already said that.
The Job system is just another system that helps you differenciate yourself from other players and their Weapon Class.
IE A Gladiator can be a Thief, Paladin, Dragoon, Warrior, Red Mage, etc.
Or a Thief can be a Gladiator, Pugilist, Lancer, Marauder etc.
It will be similar to a Job/Subjob system from XI except instead its a Job/Weaponclass system where your Job dictates your Role your weapon dictates how you perform it.