It is unconstitutional to make DC a state. If it would like to have the characteristics of a state, it can be incorporated back into Maryland where it came from initially.
The Founders limited the size of the district to no more than 100 square miles. Congreff immediately ratified 100 square miles for the district. Their intent was to have 100 square miles. Furthermore, precedent has already been set for returning land in the district to the state which originally ceded it. This would be Arlington County and Alexandria, Virginia. Currently, DC is 68 square miles. If it's determined that any further sections of the district would like to have representation in Congreff, then there is a procedure for retrocession back to Maryland. Case closed.
One other thing of note. ----If the small area that contains the Federal Buildings etc becomes the district by itself, then a Constitutional Amendment would be needed so as to remove the current 3 Electoral votes that the district currently possesses. The number of people residing in the smaller district would only amount to hundreds and would wield unequal power in The Electoral College. Case closed(again).
What they should do with D.C. is take the area and give half the land to Maryland and the other half to Virginia. Keep a few core government buildings (White House, Capitol Building, etc.) as "D.C." and have them administered by officials appointed by the legislature.
Congress should resize DC,as they have done before. Congress should make a new state with the new extra land,as they have done before. Both are constitutional and have been done before. Than make the territories states.
no taxation without representation, that is our core value. unless folks in dc are exempted from taxes, i don't think it is constitutional to rid of their constitutional voting rights, just like the blacks back in the 50s.
So could and should the residential area around DC and American Sāmoa, the Mariana Islands, and the U.S. Virgin Islands.