Best method for Skyrim-Like character customization?

you will need lots of different models. there's no simple solution. you should post exact images of what you mean, BTW.

I made something simple and unfinished once, it runs without problems and is based on prefab models.

Hope it helps!

 #pragma strict
 
 var hats : Array;
 var hatLocation : Transform;
 var hatType : String = "none";
 var hatSlider : float = 0;
 
 var hatOne : GameObject;
 var hatTwo : GameObject;
 
 var char$$anonymous$$esh : GameObject;
 var windowRect : Rect = Rect (532, 10, 400, 400);
 
 var currentHat;
 
 
 function Start () {
     char$$anonymous$$esh.renderer.material.color = Color32(0, 0, 0, 1);
 }
 
 function Update () {
 
     hatSlider = $$anonymous$$athf.Round(hatSlider);
     if (hatSlider == 0){
         destroyHats();
         hatType = "none";
     }
     
     if (hatSlider == 1 && hatType != "one"){
         destroyHats();
         hatType = "one";
         currentHat = Instantiate(hatOne, hatLocation.position, hatLocation.rotation);
     }
     
     if (hatSlider == 2 && hatType != "two"){
         destroyHats();
         hatType = "two";
         currentHat = Instantiate(hatTwo, hatLocation.position, hatLocation.rotation);
     }
     
 }
 
     function OnGUI () {
         // Register the window.
         windowRect = GUI.Window (0, windowRect, Do$$anonymous$$yWindow, "Looks");
     }
     // $$anonymous$$ake the contents of the window
     function Do$$anonymous$$yWindow (windowID : int) {
         GUI.DragWindow (Rect (0,0, 10000, 20));
         GUI.Label(Rect(20,20,100,20), "Hat Type" );
         hatSlider = GUI.HorizontalSlider (Rect (130, 25, 200, 30), hatSlider, 0.0, 2);
     }
     
     function destroyHats(){
         hats = GameObject.FindGameObjectsWithTag ("hat");
         for(var i = 0 ; i < hats.length; i ++)
         Destroy(hats[i]);
     }