Badass would've been ideal. If not Badass, regeneration would also be nice theme-wise, but unfortunately it's been discussed through and decided that it just won't fit to the game. Hmm, how 'bout... Something that'd add more durability for armor - 10 per level? - and make them stand more punishment without getting reallt damaged? Like, on the first level, all armor would give 1 AC point at minimum, even if they're in breaking point? While on the third level, even AA would always give that maximum 6 points, regardless it's condition?