CapnZapp
Legend
If my proposal was a polished ready-to-published final draft, then yes.It is Brute and Durran who are the obvious problem. It would seem they could equip themselves with a shield and gain +2 AC compared to a normal GWFer or TWFer.
Or from the other direction, Abe can pick up a shortsword and TWF.
At this stage, I'm content saying "obviously the GWF benefits require you to have both hands occupied". Or, perhaps less awkwardly, copying the language on Natural Armor or Bracers of Defense: "you gain this benefit only when you wield no weapon or shield"?
But kudos for bringing it up.