In this situation I doubt I would worry much about the service conductors.
PoCos usually size drops for a minimum of 200a anyway, it is what they carry on the truck.
I think if there is an issue it will be with the 125a rating for the buses in the meter main.
Ex3 says you can exceed the size of the service conductors but I don't think that means you can exceed the rating of the panel. It is the kind of question the AHJ should answer.
