I just don't see a trading system working. Not having raid weapons and Gjallarhorn is really a huge factor in me logging on every Tuesday to do Nightfalls, Heroics, and Raids. If I had all the gear I needed, what would honestly be my motivation to keep playing? Crucible? The economics of trading would need to be perfect. Like trading caps, currency, etc. And of course, Bungie would then need to pull resources away to figure out that structure. And what would the benefit be for traders who have all the gear? Yeah, they could trade dupes to their friends, but eventually those players would lose a lot of motivation to continue playing. Pretty sure Bungie and Activision would be against that.