You've been told, repeatedly, that this feature was removed due to cities being rendered in separate cells.
re lazy pr bs - one can buy into it or not....
I'd say the hardest part about this spell has absolutely nothing to do with cities but with scripting NPCs to use levitate. This is something I assumed they got around considering they have flying dragons in the game.
There is no way to work around it, even if you create some absurd "city dome" over every city for no good reason. This has been gone since Oblivion, and until consoles are at the point where they can handle open cities, it's going to have to stay gone.
Any large city in a world with magic and levitate (and freaking flying dragons) would have defensive enchantments and wards against attacks from above as part of their city defense. The only absurdity would be someone thinking these things are absurd.