Could you not plug a facing ratio node into a ramp with values to control the bump depth of the death star, that way the closer to 90 degrees to the camera the surface is the less the bump is on there? Think that might be what your after?

With normal maps the RGB values corrispond to the XYZ of the normal point and hold more information than just the height feild of the grayscale of the bump, they are ineffect 3 bump maps lit from different angles, X = right, Y = top, Z = down, as it dosent add geo the base mesh must have the overall shape of the underlying geo required.

I dont actually think that the base mesh on a displacement makes a difference as it tessalates it at render time to apply the map and create the polys, so the underlying form is not as important as in a normal map, although a very high displacement value will cause problems as you will run into problems with the levels you can displace.