I feel like we're running in circles but I have to ask. So if weapon doesn't matter why again does it... matter that anyone can use whatever weapon? Also the reasoning of "If it doesn't matter then why not?" is not a valid one as it runs counter to the class system that the job system itself is based on.
Also please, please stop using "past FFs" as a reasoning for why it would work in THIS FF. This game is not a previous game. We may learn from previous games but a one to one comparison makes no sense.