I do like this suggestion of maintaining some common configs.
I think people would have to step up to maintain those though, or ideally they’d be built out as VMs and use NixOS VM tests run by CI to ensure they do not break.
I also thought of making an i3-based config I’d publish, or perhaps even a “nixos-desktop” repo that shows pre-configured NixOS desktops with all the bells and whistles working for various desktop environments.