If a trade system is implemented, everyone would have everything within a month. There's not enough variety to justify a trade system. There's 20-25 unique exotic weapons. No one will trade legs since we can all just reroll till we get what we want anyway. So the only thing to trade is exotics. And with so few exotics, the game would collapse. Everyone would have everything very quickly because there are so few exotics and no one will care to grind anymore. Go out and earn your loot guardians. Stop being lazy.