So how about a ngrok like service where you just open a page to forward local traffic ? The vulnerability we've seen yesterday, "A web page can see your local servers", suggests it's doable. The webrtc code needs to open a HTTP connection to the local server. JS code would proxy all requests coming through an external hostname to this local server. Is this doable ?
"I can see your local servers" https://news.ycombinator.com/item?id=20028108