> I don't want to send a re-INVITE for that.

You should. Otherwise the remote peer would think that your video or webcam is down (black video stream of the death).

Please, if your argument is "I don't want to send a reINVITE for that" then nothing more to discuss. Welcome to SIP protocol and expectable user experience.

You could at least provide a usecase in which "muting video without signaling" is useful, and you should also explain "why signaling in that case is not desirable". And you should also explain why it is desirable that the peer receives black video screen of the death.