^^ Bending air inside the human body.. that would i think be AIR's advanced bending form that's as deadly as blood bending!!! Astig yun at malamang will be forbidden as well!
Baka si Tenzin or one of his children will learn that later on in the series(crossing my fingers)..
Guys, have you read the Avatar: The Last Airbender comic book "THE PROMISE"? Its timeline is just before the "Legend of Korra" and will explain how "Republic City" came to be.