They could do something where players can trade, but values are set (at least somewhat). For example, you want gally and your friend happens to have an extra laying around. He can trade that gally to you for a few different things. Say, 100 strange coins, 50 ammo synthesis, 200 motes. Something along those lines, and he can have options to determine what he wants, but only a few preset choices. This way, players can trade and earn gear alternatively to what bungie originally created, but it also still takes time and effort. Let's be real, it would take a few weeks (days, at least) to save up 100 strange coins whereas you can spend 15 minutes on a nightfall, get lucky, and be done. If anything, it extends the longevity of the game. Better yet, let you and your friend gamble it out over a friendly sparrow race. Additionally, to please those who think trading makes the game to easy, make the traded weapons/gear take double or even triple the time to level. You get longevity to the game, plus the player has to make a choice of whether to grind for a normal weapon/gear, or invest the time to level his traded gear. Destiny has become so mindless these days, this would make players have to think and decide for once.