In my very humble opinion, I would suggest to reserve some address space in IPv6 for rtc, so that a peer is able to adopt a new special ip reserved for rtc. Nothing new under the sun, in 2014 someone comment along this line of thought (2) and (3).
So what are we waiting for?
(1) https://webrtcglossary.com/ (2) https://www.quora.com/Will-the-IPv6-result-in-the-death-of-S...
(3) 2014, AshleysBrain, https://news.ycombinator.com/item?id=7496986 I think the solution is IPv6. Once every device on the Internet is uniquely addressable again, we can do away with these NAT hacks and two endpoints should be able to reliably connect to each other again, no matter where they are. Of course, that's assuming we don't get more short-sighted engineering that breaks things again...