Your description sounds exactly what flox is all about (and this is the announcement on discourse).
To give a rough summary: It provides a shared Nix store, where you can build your own channels/profiles, and changes to repos or to your Nix expressions automatically trigger re-builds on a remote Hydra build farm - essentially a distributed Nixpkgs setup. This also means that you only have to set up everything once, and use it seamlessly on any machine without extra configuration.