However the engine will calculate you as if you was on ground!
Other creatures would attack (or interact) with you as you was on the ground!
So (also if it was possibile) just for appareance, fly would be totally unuseless... (it could just give you some AC or attack bouns... at the max).
But the problem (especially with NWN2, than not NWN1) is that in game peoples can't detach both feet from the ground! (Even objects, as well)
Take for example the "sitting" problems with sizes. Lower size characters sits at a different height than higher one just because them didn't lift feet.
So hover is not only unuseless (if not for appareance, or some fight bouns at the max), but also hard to implement.
Creatures that already doesn't touch ground (es: bats, birds, imp and similare) are 3D builded as if virtually there was an "invisible" pole on the ground that support them (in the animation, the pole height changes). We can say that is similar than system used on real miniatures.
So to do what you say, Obsidian should modify every 3D model to have an invisible 0 height pole that should change in hover... and then add new animation for everyone of them (with more game heaviness),
