First off I think Levitation is Must, it really makes the game A true sandbox. Now it does needs some checks in places ... I will admit back in morrowind I was would chug Lev Pots and fly around with my bow raining down hell.. (but it took A bit too get too that point). I have read everyones post in this and their are a few ideas that would work awsome. One guy was talkn about .. you dont have total control over your body .... so add some Newtonian physics too it .. so if your skill / scroll is low .. you will fly around sloppy . Roll around , very hard too control. Also their would need too be lift total vs total weight. Lift > your weight + all items Weight . So a levatation potion of 140 Lbs would woker for a Caster .. but do nothing for A fighter in plate. However the total weight (mass) would effect spells length of time , air buoyancy & conrol over the Newtonian physics. The better your skill / scroll / potion the more control + speed + time.
Now with the Newtonian physics this would effect your Aim physically. Also would loved too see enemies with levitation & flight (vamps / Harpies )