Where will they move the Capital once Columbia becomes a State?
They'll have to do that, or sharply reduce the size of the actual Capital area. I believe the latter is what they plan to do to work around the Constitution. I think a more proper "solution" would be to reduce the area, and cede the remaining area back to Maryland. This is the furthest thing from what the Rats want, because they won't gain two Senators, and would only gain one or two "safe Districts" in the House.
The remaining District would be like City of Industry in CA, with little to no residences.