Selectively overwriting a home-manager home.file symlink

Hi, in my quest to integrate my non-nix dotfiles into my nix deployment via home-manager, I have had difficulties with this:

I would like to symlink all my config files recursively into ~/.config/ but also modifiy one specific file for a specific host.
I know that this is easy to achieve by nixifying the specific config file and to use variables/options etc, but I wanted to understand what is happening before doing this.

It would be something like this:

### home-manager/common.nix

  home.file.".config" = {
    source = ../../dotfiles/config;
    recursive = true;

### hosts/a-specific-host/home.nix

  imports = [ ../../home-manager/common.nix ];

  xdg.configFile."waybar/config".text = substituteAll {
      src = ../../dotfiles/config/waybar/config;
      FOO = "foo";
      BAR = "bar";

I have already tried to add force = true or = lib.mkForce ... to the overwriting statement but none of my attempts have been successful. The xdg.configFile has no effect.

Does anyone have experience with this kind of things? Thanks a lot in advance.