A "drawback" of levitation is its rarity. You can only get it from two items, both of which need to be wished for (or you do the Sumo quest).
I don't think the unability to pick things up would work in IVAN. In NetHack, levitation items are often cursed, which makes that inability an interesting problem. In IVAN, you would just take off the belt over each and every item, and be very annoyed.
I kinda like the increased knockback. That could be fun.
BTW, levitation is even better that you'd think. It also gives you a sizeable bonus to dodge chance.