A highly reflective surface might be possible on a subsonic missile. The problem with that finish is that it impairs emission of heat. A supersonic missile that gets very hot in flight would then not be able to shed its heat and that could lead to structural integrity problems.One thing I wonder about new laser weapons. What if the surface of the missile or projectile was coated with a highly reflective mirror finish?
Some kind of ablative material might be a better alternative.