[NixOS] buildFHSUserEnv for special binaries?

Technical Discussion
#1

Dear holistic tribe

Do you use NixOS’ buildFHSUserEnv (configuration.nix) for special binaries, e.g. self-updating apps like Firefox Nightly?

@see https://nixos.wiki/wiki/FAQ#How_can_I_manage_software_with_nix-env_like_with_configuration.nix.3F