My family and I were seated in Biz trans atlantic and a family tried to do something similar to this (but they did it before take off, rather than mid flight) - the purser caught it during their pre-flight check... it delayed out departure because the lady WOULD NOT go to her assigned seat and wanted to argue... The Captain finally came out and said, you have 10 seconds to move to your seat or I'm cancelling the flight and you're going to jail...

Honestly, like others have said - it's a hard no..