If Maryland made a special constitutional amendment that could only be changed by a vote of the people of DC and they granted

1. Total self governance, DC can make and enforce and laws and taxes it wants within the city, and doesn't have to follow laws or taxes of Maryland.
2. All Licenses and certifications will be accepted from Maryland to DC and DC to Maryland
3. DC will be its own congressional district, its own electoral college district and have its own districts for the state house and senate, with a rule that it will never be split up or become a minority of another district.

what you're describing would require congressional approval and changes to the u.s. constitution which requires much more than that (super majority of congress + 38 states), not just state of maryland's.