Nice! It looks essentially like userspace NAT, only active for particular ports. I'm contemplating a similar setup to handle access to my home machines: when I'm in my home network, some ports are forwarded to 127.x.y.z directly from the remote machine, and when I'm away, the same ports are forwarded via a Wireguard connection. This way, at home I can use the full speed of the LAN, and when away, the speed is limited by the Wireguard gateway, but I still connect to the same host:port, wherever I am.