If congress allows a mayor and a council, is it still unconstitutional? Depends. Does "exclusive" mean "exclusive"?
Exclusive: not shared : available to only one person or group
Interesting. I've never really looked hard at this issue before. On it's face, you appear to be correct. I'd like to read some of the laws that congress thought they used to get around the Constitution.
Thank you for bringing that subject up. I haven't studied that 10 square miles part of the Constitution nearly well enough. Mea Culpa.
/johnny