Eventually it is clever to allow brawlers to enchant gloves (not armoured gloves but normal from leather or something) such a glove will not stack with weapons in the hand.
I.e. I wear a longsword +1 and gloves +2
attack on second level with 2wf dealing 1d8 +full str bonus +1 and 1 d6 offhand + full str bonus +2
Or special arm jewelry? Braceletts? I don't know the word.
Edit: or allow brawler to deal his unarmed damage with armoured gloves and this other weapons that doing the same sort of damage (bludgeoning)