Just a follow up to my post--so Singapore Airlines did allow my wife to come up from business class to first class for a while (route SIN - FRA). I actually didn't ask but they offered it. They were so awesome throughout the whole route and even allowed us to swap seats from the FRA to JFK route. While I was in business class on the 2nd leg, they even brought a glass of Krug to me (I didn't asked, but my wife sent it).