Hyundai offered air suspension in certain export models that are not sold in USA. A middle eastern friend told me that there were 3.8 Genesis with air suspension sold in Iran. I suppose you could convert your USA-spec, but the cost would be huge.
I have an Equus with air suspension and had four Genesis. I think the Equus suspension is fairly smooth, but not materially smoother than the any of the four Genesis I previously owned.
There are aftermarket vendors who sell air suspension kits, but they are not cheap either. Finally, it appears to me that the new Genesis G90 will not have air suspension. Perhaps there is not enough room because of AWD.