Really good idea, seconded.
But consider this. If that player is muted, instead of kicked because of his language, flaming, general behaviour etc., he will not know that he is indeed muted. Hence, he will come back to the same server, admin maybe wont be on at that time, so he will continue with his behaviour not knowing he was muted before. With kick/temp ban, admin states that that kind of behaviour will not be tolerated.