Trading - Been suggested 100s of times before, never going to happen.
2v2s and 3v3s - update will come out in a week or so. More on that http://youtu.be/7PxXceQaFDg
Durability - ehh, would probably kill the game.
Anytime you see a weapon with "Mark 1" after it, you can always expect there to be a mark 2 version or higher.