Hello Heiko, agree with bjoern, sounds interesting and welcome 
Our tentative ide was to allow configuring a WebRTC server for a Delta Chat app and to introduce UX to “share” (post) a webrtc config with chat partners so that they can also “use” it. Once configured one could perform WebRTC audio/video calls with chat partners even if the other side does not have webrtc configured. One could also setup a call with regular e-mail users (say someone using webmail), which would simply arrive as a webrtc link. If you want to start on this we could see if you could join one of our dev gatherings that we regularly do in Freiburg.
The topic of routing messages over WebRTC instead of e-mail i’d leave for later. There are several open questions (multi-device, device-to-device sync, …) and it’d be a somewhat major refactoring on the deltachat-core side which is also currently changing quite a bit in other ways.
cheers holger