TVNZ would not be able to create its own mission statement. It is required to deliver the Charter under the TVNZ Act 2003. Any change would require legislation. It is no longer an SOE. Its mission would have to be agreed with its shareholding Ministers ie the Government. National could not avoid responsibility for the decision as to what TVNZ's mission should be.
My view is that doing away with the Charter and TVNZ's dual mandate simply allows an unregulated commercial free-for-all, in which viewers and the public interest, will be the losers.