Something else to think about if you NiteShade the inside of the lens...
You would be applying the coating to the inside of the lens. The perimeter of the lens will be glued back on to the reflector. Unless you leave a band of unpainted plastic around the perimeter on the inside of the lens, you will be gluing the NiteShade (not the lens) back to the reflector. Of course, that would mean that you'll have a dark lens when seen from the outside, with a bright red band around the perimeter.
I wouldn't expect that bond to hold up over time. I wouldn't expect the lens to fall off, but as the adhesive pulls the NiteShade off of the lens in some spots along the glue joint, you will get moisture penetration inside the lens.
It's a good idea in theory, but it has its drawbacks...
2003 Ford Ranger | FX4 Level II | 5-Speed Manual
A few minor mods... nothing cool enough to mention.