I’m actually not a fan of this idea, sorry. I understand that you sometimes want to report people or have some time for yourself, but I doubt that your chat is flooded with friends who are constantly messaging you to team up. I personally find it quite simple to just say: “No sorry, I’m busy right now/not in the mood to play.” My friends would be okay with that because I will play with them later.
Besides, friends are people to talk to, to hang out with in the lobby, and to play with. By adding this, a lot of people could set themselves to offline. I personally would find it a pity that when I’m looking for someone to play with, half of my friends who are actually online, are now set to offline without me knowing. Also, just imagine you’re joining a game and you see a friend in that game as well, who set themselves to offline. Wouldn’t that be a little confusing?