It is not that unheard of to do farewell flybyes at Paine Field gear up down to ground effect. I certainly remember some different ones with quads. It's not aerobatic and should be perfectly safe and acceptable on a ferry flight without paying pax.
I have heard this one only became an issue because the CAA of Hong Kong hadn't been asked beforehand. As it had become known in public there was no other way out of it anymore.
PS: And here's a new german operator of the 777F looking for 200 experienced pilots. Might be a place for the sad skipper.
www.aerologic.aero