Would your city want one?
I cannot think of anything less that cities such as Leeds, Birmingham or Manchester would want. These places are confident in their own right, all they want is a fair crack of the whip.
Take out The City with its banks and spivs, take out central government and its ministries and overpaid civil servants, take out the Royals and their undeserved influence and you will find that the average Londoner is no more or less dynamic than the rest of us.
It is a bloody insult to appoint a minister to a city or a region. Making sure that the spoils are more equally shared out would be a better option.