the film while being a great idea, would not work due to the fact the visor has curvature, and shapes that a flat piece of self adhesive tinting would not work well with (ripples and such, as well as obvious seams if you cut it to allow curves)
the visor within a visor sounds like a good idea, but i know some people have made a visor with a mirrored effect for master chief, so it stands to reason theres ODST methods as well.