If they wanted it to be an "Earn you gear" thing they could introduce a trading tariff. Basically it costs X amount of Strange Coins/Motes/whatever(As long as it's rare enough you only have a few) to do a trade. The game just takes the coins. Basically it'd be treating it as if the other player was a vendor (Like Xur). Except nobody would recieve the strange coins on either end. They would just disappear. Leaving both players to receive whatever armor they traded for. I understand they don't want going from 24 to 28 to be as easy as "My buddy through some gear my way". So this is just an idea that means players will have to work for the gear still. As for duping. Yeah, any method would have to be dupe-proof.