The trading discussion's been done to death. Needless to say it would create problems if players could trade items willy-nilly.
My alternative: A special shop where you can exchange your epics or legendaries for different items of the same rarity.
Items for trade refresh weekly
The trades would be e-m to e-m and premium to premium, no e-m to premium
Due to lack of utility and/or being easily attainable, any item below e-m would be excluded from both the shop and the player's items to trade (ie nightmare, sith, banshee, chimera, etc)
There would be an additional fee (coins or tokens) for the trade so players don't trade out their trash for op items with no cost
The cost would be higher for premium trades than e-m trades, and higher for legendary trades than epic trades
Not something I need added to the game, but better imo than unrestricted trading with other players.