How about you pay for "premium" in here and if two people have it, you can trade? You can normally trade up to legendary weps, but past that if you wish to trade an exotic you must possess an exotic for exotic on top of 5 exotic shards on both ends. This way it's more of a hassle and requires you to somewhat earn the ability to trade, I don't see much difficulty in it either, to trade the raid legendaries you must also trade the 5 shards, for raid exotics, 25 exotic shards, that seems pretty fair Edit: if connection is lost on either end during trade, items are lost forever