The feature WebRTC as RTSP is not so popular. So we did not have a chance to investigate it due our internal schedule.
I believe we will able to do it bit later. Maybe when the issue will collect some votes or when we will have a window in our schedule. If we have a progress here, I will update the thread.
Regarding the second issue related Audio Call and Answer with Video.
We have investigated it and partially fixed. However we have released that it does not work properly with latest Firefox browser due Firefox WebRTC bug.
When Firefox receives SDP with sendrecv in audio and video sections but does not have video, audio will not play. So in the case when we make an audio call (audio=sendrecv, video=sendrecv to be able to answer with video), and then answer with audio only (simple audio call), caller does not receive video and Firefox does not play audio. Therefore simple audio - audio case is broken.
We are going to continue this investigation when Firefox with session re-negotiation fixes will be released. Currently we recommend answer without audio to audio calls and anwer with video to video calls.