Some form of chat or in game communication method is needed other than the limited fire team chat. As for trading the only logical method of trading I could see implemented is a timed trade window for drops only to those who were present when the item was picked up.
English
-
They should of made it like red dead redemption where you can hear people if they are near you but if you go farther you don't hear them, but you can always hear your fireteam no matter what distance!