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This is actually pretty important. I second this request as Unity relies on some specific variable names to drive other things.  From the documentation:
  • Self Illuminated materials will emit light tinted by the Color and Main Texture and masked by the Illum texture. The intensity of emitted light is proportional to the Emission property (0 disables emission).
I know from experience that if something is not "_Illum" and "_MainTex" in the shader, Beast won't like it. "_EmissionLM" is another variable that dictates the intensity of the beast illumination. I wish they didn't hardcode this stuff but there it is.. There are definitely more.