If you modify the demo and it doesn't do what you want, then you've introduced a bug :-).
The multiparty chatroom demo is based on the easyapp framework which makes certain assumptions,one of them being that connections are symmetric (video streams are shared in both directions). If you to violate this assumption, its probably easier to start from bare easyrtc. Note: be aware that you'll still have fan-out limitations due to the full mesh model running into your upload speed.