Sarah has already incorporated into the module penalties to folks using necromancy spells. Every time you cast a necro spell your aligment shifts 1 towards evil. It would be interesting to see if your suggestion would work, for instance making it so evil clerics/paladins are completely unable to use any spell with the "cure" keyword (light wounds, serious, etc) and the spells heal and mass heal. Maybe a shift in good alignment for clerics for casting cure spells would be appropriate? Or maybe spells which have effects related to alignment could somehow be linked to your alignment (weaker the further removed you are from "pure" aligment (i.e. when you have a specific alignment title). I dunno..interesting thought tho.