I know that GMs watch out for each other. Not like we're all watching to see when another screws up, but believe it or not, some of us believe we have a sort of duty to help out the players and only the players. If someone is thought to be making mistakes, or purposely abusing something, then they are talked to.
I think the current system is better than creating one person in charge of oversight because the current situation has several different options in terms of oversight, this includes Talad and the Dev team, along with Players who may be mistreated or ignored, etc.. If you put one person in a position, i think they will become too powerful, not to mention swamped with petty complaints that may have no validity at all.
Hypothetically, if this was created, i think we'd have a problem finding someone who would be able to/want to do it.