Monsters should never read scrolls of earth in Sokoban, given the high chance of messing up the puzzle. Possibly, they could be allowed to read it after the puzzle is solved and the penalties go away.

Add a level flag for the level being open to the sky or otherwise no ceiling. Effects of this include: falling rock traps do not generate, cursed potions of gain level do not work, scrolls of earth do not work; monsters that normally cling to the ceiling are unable to. Levels that would have this: lots of Quest levels, the Elemental Planes.