i think we're forgetting to take in account tribe alignment. this aspect could have effects on items(certain weapons &c) also causing more trade between tribes and use of strategic trading(more dynamic economy)
there are already many mmo and RL examples of armors countering things likeso "special armors" wouldnt be neededa club with knock out properties that would disable a player.
padded/leather
i think another awesome and different addition would be creating a system that gave players who, perhaps, picked a more defensive path and have the ability to gain small defense bonuses against attacks used the most on them(learning) or a small resistance to certain blows on areas. pretty much an adaption skill. the possibilities of it would be great