Let me throw this out there, how about WAR picks up a Beast-men grip <JT> that allows them to single hand wield 2 handed weapons and allows them to use a shield at the same time. You could add a penalty in there to balance it out and introduce some new gear that would make you more effective at it. Or you could go the merit JT route with it. Other FF games have had this JT and even beast-men can be seen in the game swinging 2 handed weapons around with 1 hand.