Well, I may be misunderstanding you but your description made me think of a technique I heard of a while back on how to make something look more metallic (that was part of it anyway). It was all done with curves and I believe it was starting from grayscale images but it would seem to me that a desaturated image isn't all that far away from a grayscale anyway. Above is a before and after. All that was done was the adjustments shown. Curves (to flatten out the midtones (desaturate) and add a little metalic feel to it and then Levels to boost the whites and blacks. If that was not what you meant or if this approach doesn't get you any closer, my apologies. If nothing else, it's something else to play with.