What they can do is make it so you can only trade items that have dropped when you were in a fireteam with said persons. The division has this in the game. I have had multiple times a exotic dropped after doing a mission and i dropped it or traded it to a player that what in the group I was in. And i think you have like a 2 hour timer to do so also says what 3 people you can trade it to. Bungie can do that same thing.