Till then, if the darkness is annoying, type 'rimod xx000800' into the console, xx being the load order.
To get it back, type 'imod xx000800' into the console instead. I will also make it such that you can toggle it ingame.
Forget all that! ^ \o\
In version 1.1, the game will switch between two overlays: the exterior one and the interior one.
However, if the overlay still annoys you, you can do "set OverlayACTIVE to 2" then "rimod xx000800" if you're in an exterior cell or "rimod xx002943" if you're in an interior.
To get it back, just type "set OverlayACTIVE to 1".