This is great! I've had this exact idea for a specific robotics use-case but never got around to implementing it: a fleet of robots that each expose an HTTP service for debugging purposes. These robots connect to the internet through cellular or hop around among a set of wifi access points, such that long-lived connections are often interrupted and each robot IP address intermittently changes.

Many other reverse proxy / tunneling solutions use TCP-based protocols or require the target hosts to be accessible by the proxy server, but in this case QUIC connection migration avoids the reconnection handshakes needed for dropped TCP connections, and your client->server model allows the robots to register themselves from restrictive networks.

The only missing feature would be to allow some sort of auth plugin - perhaps as a sub-request made to an external auth service that contains the identifier of the client the request will be routed to, similar to nginx's auth_request (https://nginx.org/en/docs/http/ngx_http_auth_request_module....)