[Crow]

I think more layers should be added. If you dont want everyone to rewrite their scripts, you could just add negative layers, and (mabye) set the player default somewhere in the middle. (Example: layers from -50 til 4 (and above 4 of course). 4 and above are screen orientated, the others tile orientated. Player would be set to -25 or maybe lower, so you can easily place a lot of things under and above the player.)
Wouldnt fix the poly-lighteffect thing, but it would be a neat addition for sure.