I am very much for the idea that one would choose a role/title to superimpose on thier current class. In this we dont really need role specific weapons. Plenty of room for more classes to be released.
The role is worn like a state of mind... or maybe eventually armor. Something akin to ffxi's artifact sets. With that i would expect limitations governed by class, preventing a Conjurer from running around in Thiefs armor. That is not to say you couldnt be a Thief with a wand. Armor like this would only serve to further boost specialization with whatever role-enhancing qualities it might have.(+3% cure potency WHM hats) Can even throw class specific armor into the mix with its own weapon/spell enhancements. Maybe? (Enhances Steadfast effect shoes)
People seem to be concerned with getting locked into optimized builds but i feel like this will mostly always be in relationship to party size. In a four person party, depending on the task at hand, there is a good chance one wants to play as more of a hybrid. Larger partys afford themselves room for more specialized roles.