Kerbal Space Program

Unlike the Unity Standard Specular shader it is based on, Bumped Specular (Mapped) has only a slider for shininess instead of pulling from the alpha channel of the specular map. this makes it difficult for one mesh to have a metallic material next to a non-metallic one, like on the carbon nozzle extension of a rocket engine

I propose passing (specular.a * _Shininess) to the BRDF, to keep backwards compatibility with anything designed for the current version of the shader, since any specular map without alpha the game engine will sample the alpha as 1.