Would be fun to have his own personnal airship as a house (or a boat) even if it doesn't fly on the map.
Anyway, with the zone and loading screen, i don't think flying would be nice to have.
It would be simple as a mog house, just add a small cut-scene when you enter the airship port that take you on sky and get you to your own ship.
And i see there, a good way of custom it. outdoor like indoor !