Not something I want the devs to spend time on. If they did implement it I would turn it of asap, and if I could not turn it of I would seriously quit the game.
The current third party voip programs are good enough, there we get to decide who we want to talk with and when.
If an in game system was implemented it would.
1: Take resources away from other things.
2: Result in us having to hear some 12-year old a-hole screaming in a squicky voice how they are going to f*** someones mom. And we would hear this a lot all over the place. Better to leave that animal in its natural habitat, CoD.