I have NO idea what your concerns are. None at all. So far, you've stated a federalist paper, but that paper is about patents and copyrights and doesn't include anything about DC that could form the basis of a modern day concern. Maybe you should try to create a scenario in which Madison's concerns become a serious issue were DC made a state today. In your worst Madisonian dreams, what is it that you think would happen?
I'll answer any individual argument you want to make, regardless of your source. I'm certainly not going to sift through a federalist paper to guess at what you might think is a valid point. Let's remember that everybody agrees that there will be an exclusive federal district that is not part of any state. That is not the issue.
Why not add Guam and the Virgin Islands, American Samoa and the Northern Marianas? Might as well go for it, 2 senators each. that ought to freak out republicans. Hah! Don't we have bases on some of those? ( I know we have one on Guam ).