LEAVE IT to Marion Barry to come up with a dramatic way to mark the plight of homeless people in the capital city as the season of bitter cold approaches. Last Thursday the mayor personally took in 73 people he had gathered from disparate streets of Washington -- giving them warm welcome, new community status and access to the corridors of the Reeves Municipal Center. They will be welcome there from now on for what apparently is an indefinite period of time. As it happens, these 73 people do have shelters of their own to sleep in by night. Believe it or not, this crowd is a committee: the new Coordinating Council on Homelessness, which replaces a tiny 23-member panel that reportedly has been advising the mayor on homelessness for the past five years.

The idea behind this latest community roll call, we're told, is to establish a council with a more visible role than that of the tight 23. There's no arguing that this new megapanel, by its mere assembly for swearing in -- is visible. It may be divisible, too, if experience with groups this size is any indicator. The members' responsibilities are supposed to extend beyond reviewing policies and legislation dealing with the homeless, to include actively coordinating various private and public programs.

There's nothing wrong with enlisting the best minds and money in the city to help improve the lot of the homeless. And Mayor Barry's choice of developer Oliver Carr to deliver private assistance from around the city is a good one. Mr. Carr believes that private interests have not provided all the help they could and says he'll call on them to "come on board." That's fine, and perhaps the official enlistment of those 72 others willing to serve in this volunteer group will make a difference. Let's see -- there are about 6,500 homeless people . . . that's only 89 or 90 for each council member . . .