Hey i like this idea, and don't worry about you're concept drawing, it doesn't have to be GOOD but it does still help alot and i'm glad the SM people are trying to get us in the habit of it. I think you're idea about the head is great, make the metal work very simple
, and you can save alot of time modeling, and spend it all texturing. Maybe think about using some reflection, but very dirty reflection(only patches of it)