I think the proper term to describe this potential shift in authority is, bestow. The fact of the matter: Coach McCarthy will not be laying down his sword; rather, he is entrusting his power to the hands of another. The men his successor will be commanding will be the same. The tactics this man will be using to command them will be the same. And in the end, they all swear fealty to McCarthy. "I think armies give you power".
I neither agree, nor disagree, with this prospective change. However, I think it shows prudence on behalf of McCarthy. He is able to look at his performance in battle and reflect on it, critique it, learn from it. Coach McCarthy is able to celebrate and recognize where he has prevailed, and yet, he can also acknowledge where he may have had shortcomings. "Once you've accepted your flaws, no one can use them against you."
I liken this move to naming a Hand of the King. The Hand of the King is the most powerful position on a team's offense. He claims the full trust and authority of the King. His station allows the King to address matters elsewhere, as he sees fit. The Hand also makes decisions on the King's behalf at the Small Council, and yet, he is always and forever beholden to the King. Instead of being an independent voice and an instrument of free will, he is a proxy...albeit one of great power. Any act that is not like-minded and meeting the King's approval, will be amended swiftly and, presumably, with great vengeance.
Ultimately, it doesn't matter whether you celebrated in Flea Bottom or scoffed from the Red Keep at this potential change, when you play the game of thrones, you win, or you lose. There is no middle ground.
The King is still the one in power, and he is still the one playing the game.
...also, "It's not easy being drunk all the time. If it were easy, everyone would do it."
