well SE can always do anything they want to the system, there already scrapping what we got now who knows whats comming later, most likely end up a ffxi-2 when there done.The Mages Weapons are actually how they cast AOE when they cast an AOE Spell. the Equipped Weapon is just a focus It helps them channel the energy into the cast.
Thaumaturges weapon is Cone AOE
Conjurers weapon is Circle AOE.
The differences between their Two hand and One hand equipments are null at that point.
This isn't even the issue. The issue is things like being able to be a Melee oriented PLD to tank based on damage dealt not just defensive skills. Marauder has defensive skills too.