I think it would be neat if we could have dark and light or evil and good versions of the same spells. There could be a spell affecting plants, where the dark version would infest a plant with weeds and insects, degrade a plant's quality back down to normal, or even kill a plant while the light version would cure a plant, cause it to bloom or fruit, evolve to a higher level of quality or revive it when dead. Obviously, good spells could clear or dispel bad weather (with a few new good varieties, like calling up a rainbow or causing an increase in blooming or rate of growth in plants) while bad spells could invoke terrible weather, deadly lightning strikes and plant-killing cold out of season. Or have sims cast a positive spell to raise friendship or love levels to max, as well as a negative version to degrade them to zero and create an enemy status instead; spells to drain or fill Sims motives (including the hunger motive) could be effective, or to inflict or cure illnesses in pets or sims, as well as to call up or banish pests of various kinds. It would be neat if all these spells had nice effects as well as new moodlets and whims arising from them.
Like someone else mentioned, I'd like to see the ability for witches to enchant certain objects, but make them function in ways either good or evil -- for instance, a Mary Poppins type spell for cleaning up dirty dishes, books and toys, and repairing broken electronics, could have a dark version which would make even more of a mess and break even more electronics. Good sims could enchant toys to play with and amuse their kids even more, while bad sims could enchant a toy to cause mischief, stalk, scare or otherwise bother child sims. Let's have sims cast spells which would make a sim cook excellent dishes, paint flawless masterpieces or write bestsellers, with a negative version whereby the quality of every meal, painting or book created by the enchanted sim would be much less, either normal or poor. On reaching the most powerful level of magic, a good witch could even have the ability to raise a sim from the dead, bringing them back to their normal selves and even younger (if they died of old age), while a bad witch could bring back a zombie with a very altered personality and a permanently angry emotional state. It might be fun to have a cornucopia spell, which, in its good version, would cause stoves or fridges to produce quantities of excellent level dishes (with extra servings) while in its bad version would empty their inventories and cause them to produce smaller servings, poor quality or even spoiled food which would make sims sick if they ate it. A spell to add nice things to a sim's inventory as gifts could be a thieving spell to steal from sims' inventories in its bad version. I also love that someone mentioned of Swan Lake type spells to enchant sims to take on an animal or occult state at night while remaining human during the day; a good version of this spell could cure those type of enchantments or protect against curses.
Some Harry Potter-type spells to turn invisible, duel another magical sim with a variety of curses, change a sim's appearance to mimic or copy another sim's appearance, turn back time, start or put out fires, summon objects or send them away, turn into an animal at will (a controllable one) and change back, and fix or break objects etc would also be welcome, but these would be more neutral spells rather than positively good or definitely evil ones.
