made some progress

modules/nixos/default.nix

@@ -0,0 +1,42 @@
+{ config, lib, pkgs, ... }:
+let
+  inherit (lib) mkOption mkMerge attrNames filterAttrs;
+  inherit (lib.types) nullOr enum;
+
+  cfg = config.${namespace};
+in
+{
+  options.${namespace} = {
+    preset = mkOption {
+      type = nullOr enum [ "server" "desktop" ];
+      default = null;
+      example = "desktop";
+      description = "Which defaults profile to start with";
+    };
+  };
+
+  config = mkMerge [
+    (mkIf cfg.preset == "desktop" {
+      "${namespace}" = mkDefault {
+        hardware.has = {
+          audio = true;
+        };
+
+        boot = {
+          quiet = true;
+          animated = true;
+        };
+        
+        desktop.use = "kde";
+      };
+    })
+
+    (mkIf cfg.preset == "desktop" {
+      "${namespace}" = mkDefault {
+        services = {
+          ssh.enable = true;
+        };
+      };
+    })
+  ];
+}