It may not be possible for either code reasons or just CPU efficiency, but could this mod add the light radius decay code from artificial light sources to natural light/sunlight? Can't tell you how many times I've built some overhanging roofs from a structures edge forgetting that the game treats outdoor roofs as total light blockers... hilarious how light is treated as coming straight down; all umbra, no penumbra!

Well, or Tynan could fix it in vanilla, but if it hasn't happend by now, it ain't ever gonna happen!