That doesn't make any sense. The purpose of voting as a citizen of a state is to have representation that, one hopes, reflects the needs of you and your neighbors. Allowing them to pick "wherever" would effectively dilute all of those votes, wherever they are being sent, and someone in DC voting, for say Georgia, is never going to be represented by any legislator in Georgia.
If you mean either VA or MD, that could maybe work. ....would certainly piss off a lot of southern, western, and eastern VA, that's for sure. 😀
DC pretty much commands a heavy influence over those two states, anyway, much to the consternation of the more rural, highly conservative boonies of those states. MD is pretty much unrecoverable for the GOP, even as rural and agrarian as it is. sending DC votes to VA would do the same for that state. and it's not like this is a unique model in a lot of states: Chicago's commanding influence over all IL politics; NY city in NY