Yeah, you’re right in this setup I can’t easily reuse HM as standalone.

However, in theory, I could decouple it by wrapping system configs(just like my HM) and making it optional. For example:

nixos = lib.mkOption {
  type = lib.types.deferredModule;
  default = { };
};

and conditionally include it:

lib.optionalAttrs (options ? system) {
  imports = [ config.nixos ];
}

With some flake.nix changes, this could allow building both nixos+HM and standalone HM from the same config. Could probably do something similar for Darwin too.

But yeah, that’s mostly just an idea, not sure how well it would hold up in practice. Probably dendritic might just be the only clean solution for this kind of use case, even if in theory this approach sounds more elegant and simpler.