Maybe a useless post since it's not what you asked for but as I was reading here I wondered if a 'helium balloon with a rubber band' effect might be nice. The camera would float over the player, looking down at him, when he runs / walks depending on the speed the camera floats down to be a chase cam. When he stops it floats back to its overhead position. The 'rubberband' part would be the distance of the cam from player as he runs faster the camera distance stretches. When he stops it snaps back to original distance and of course slowly floats back to its overhead position.