Remote Builder push OCI image to external registry // Docker Engine over the network?

Hi, how can I make builder to push OCI image to external registry instead of
Remote Builders are sharing their Docker Engine over the network, but the way that flyctl build an app is either: Buildpacks, Dockerfile, or Nixpacks and after the build process it just pushed the image to’s registry, and run it (optionally, I am using --build-only).

However, since the Docker Engine is exposed and there’s built-in proxy that able to mount it as a UNIX socket, we could do anything more than that, opening the possibility to extend the usage of the remote builders, eg. make it join a Swarm network, or running multiple containers at once, etc etc. I have working proof of concept here: GitHub - ii64/flyctl at feat/remote-builder

Thank you!