Here's how Xur should work. He sells each ACCOUNT 1 exotic engram per week, for 25 (yes, TWENTY FIVE) strange coins. You get to choose whether you buy an armor or a weapon, but since it's an engram, you don't get to choose the gun or armor you get. The exotic engrams would also not differentiate between slots- so an armor engram could decode into a chest, a helmet, whatever. Likewise, a weapon engram could decode into any kind of weapon. You get one shot per week per account. No more. So, let's say you save up, spend your 25 coins, buy an engram, and get an item you don't want or already have. You can trade that item back to Xur for 10 strange coins and an exotic shard, and try again next week. This would allow everyone to accumulate exotic weapons and armor, but would retain the "exclusivity" of the items, because not everyone would be able to just buy [Exotic Gun] every week. You'd treasure each new exotic more, and use the ones you have like the awesome weapons they should be, instead of the commonplace "shard guns" they are now. The engrams costing 25 strange coins would also ensure that players couldn't usually buy an engram every week, making each purchase even more risky and each reward more sweet. However, it would also remove the need to "OMG HE HAS ICEBREAKER QUICK GRIND COINS" because he'll have the same engrams for sale next week when you have the coins. Bungie will never do this, sadly.