An agile edge case should be a temporary catalyst to cut teeth and lead to full blown agile adoption, otherwise agile is pointless.

I've been a part of couple of cargo cult teams in the past few years and it's really frustrating to try to get others to think in Agile terms. Having an agile authority to help enforce various agile methodologies is beneficial when sometimes you're ignored as a piddly code monkey.

I would be very careful with that position. It presupposes that a centralized knowledge-base is necessary for true adoption. If nothing else, this gives you a central point of failure. Also the word "enforce" gives me the heebie jeebies. Don't like seeing "enforce" and "Agile" used in the same sentence :)

How about his? "Having a trusted outsider to make non-binding recommendations about Agile practices can remind us that if we don't follow Agile practices, we're not going to get any improvement from Agile."

Most Agile adoptions, even ones with Agile authorities, achieve only a 5-10% improvement. This is because it's all too easy to give up on the team and take control, whether you're doing it for Agile or non-Agile reasons. You end up killing the very thing you're trying to promote.

EDIT: The only exception I would make to this is if the team really doesn't understand what they are doing, yet are convinced it's a bad idea. In that scenario, usually a coach or somebody can help teach the team (by insisting they try something) until they know enough to make their own decisions.