Nix config list ++ list attempt

configuration.nix

# ... some things here ...

 environment.systemPackages = let
    basePkgs    = import "${configDir}/pkgs/basePackages.nix" pkgs;
    devPkgs     = import "${configDir}/pkgs/devPackages.nix" pkgs;
    desktopPkgs = import "${configDir}/pkgs/desktopPackages.nix" pkgs;
    networkPkgs = import "${configDir}/pkgs/networkingPackages.nix" pkgs;
    vim         = import "${configDir}/pkgs/vim/default.nix" pkgs;
  in
    basePkgs ++ devPkgs ++ desktopPkgs ++ networkPkgs ++ vim;

# ... some things here ...

pkgs_vim_default.nix

{ pkgs ? import <nixpkgs> {}
, stdenv
, lib
, writeTextFile
, writeText
, buildEnv
, fetchurl
, fetchgit
, fetchFromGitHub
, ...
}:

let 
    plugins = import ./plugins.nix;
    vimrc   = import ./vimrc.nix;
in
plugins ++ [(lib.overrideDerivation pkgs.vim_configurable (o: {
    postInstall = (o.postInstall or "") + ''
        ln -sf "${vimrc}" "$out/share/vim/vimrc"
    '';
}))]

pkgs_vim_plugins.nix

{ stdenv
, lib
, writeTextFile
, writeText
, buildEnv
, fetchurl
, fetchgit
, fetchFromGitHub
, vim_configurable
}:

# copied from aszlig, thanks a lot!

let

    fetchVimScript = { srcId, sha256, type, name }:
    let
        baseUrl = "http://www.vim.org/scripts/download_script.php";
        src = fetchurl {
            name = "script${toString srcId}.vim";
            url = "${baseUrl}?src_id=${toString srcId}";
            inherit sha256;
        };
    in stdenv.mkDerivation {
        name = "vim-${type}-${toString srcId}";
        buildCommand = ''
            install -vD -m 0644 "${src}" "$out/${type}/${name}.vim"
        '';
    };

    extractSubdir = subdir: src: stdenv.mkDerivation {
        name = "${src.name}-subdir";
        phases = [ "unpackPhase" "installPhase" ];
        inherit src;
        installPhase = ''
            cp -Rd "${subdir}" "$out"
        '';
    };

    mkVimPlugins = plugins: buildEnv {
        name = "vim-plugins";
        paths = with lib; mapAttrsToList (const id) plugins;
        ignoreCollisions = true;
        postBuild = ''
            find -L "$out" -mindepth 1 -maxdepth 1 -type f -delete
        '';
    };

    pluginDeps = {
        vimPlug = fetchFromGitHub {
            owner = "junegunn";
            repo = "vim-plug";
            rev = "ebe8635043a068197b41d757db6b549c1e1caa87";
            sha256 = "20056d12f1e9cc170ca49b156267635c83d5e54c3a9803c24dd44970390751ab";
        };
    };

    plugins = mkVimPlugins (pluginDeps // {
        vimYouCompleteMe = fetchFromGitHub {
            owner = "Valloric";
            repo = "YouCompleteMe";
            rev = "13266679edd9a3e8cb0f067e6eaa1905914c6fc2";
            sha256 = "67e48da1ed88c2ecd542f5b3b5b84c02ec5a0fa0eee540cb8835d3f36dc1bea8";
        };

# ... more ...

    });

in
[
]