I know I keep stressing this but I want to get the idea out there. This would speed up the process a little for those of us that can't play a the time (college, military, traveling jobs etc.)
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I don't think that Bungie will add any sort of training/auction house because of Xur. He's sold too many exotics which would ruin any sort of economy. In my opinion the original way of getting loot from engrams actually leaned towards a trading based game, as you had to roll the dice twice; once for the rarity of the Engram drop and another for the decryption.