> Using a different language to depend on packages derived from .nix would be very much akin to depending on a docker image whose Dockerfile you can not inspect.

Speaking of Docker images and Dockerfiles, that's actually a real-world example of how you can achieve this kind of effect without relying on a specific language. Ironically, you can use Nix to build Docker images; there's a bunch of other alternative builders (e.g. Kaniko, Buildah); you can also just stitch together some files&metadata into tarballs, and then 'docker import' it.

Nix or Guix are of course much more powerful and expressive than Docker images, but there's always a cost to complexity.