I've tried Supreme Magicka, LAME and Midas Magic, and all three of these magic overhaul mods are outstanding (kudos to their respective creators!). However, I have noticed (or have overlooked) a spell from D and D that is absent that I would love to see implemented:
darkness, n foot radius. For those that may not know, it generates a sphere of complete magical darkness that cannot be seen through with normal or even infravision. This would be awesome to see in action in the game, but I'm not sure that the AI in Oblivion would react appropriately - would they stumble blindly and swing madly, or simply know where you are no matter if they were blind or not?