A button for leadership orders

There are different voice channel and each person can talk freely(like there are 5 people on team 1, 5 people on team 2, 5 people on team 3 with leader on it). It would be cool if the leader can press a button to command all teams to attack or defend something, while other teams communicating they can hear their leader whenever he press the button. I think that would be a cool feature and would be really helpful for mmo players etc.