The current owner of the land that the plaza part of L'Enfant Plaza occupies plans to replace it with yet another office block. A far higher use of this land and one in keeping with the objectives of this project would developing it as an extension of the Mall that would provide would provide a sheltered space for the sort of activities currently conducted on the Mall itself (festivals, etc).
GSA: Get creative in working out a swap with the real estate developer who currently owns this land. Possibilities include swapping the USPS headquarters which would then be re-developed and used for purposes in keeping with the plans that would most improve this area -- e.g. a mix of retail, residential, and hotel use. The USPS is an organization that is really hurting economically. It needs to get very serious about unlocking the value of its enormous real estate assets and what better place to start than with its HQ building. It could get new and better headquarters at a re-developed Main Post Office Building at North Capitol Street and Massachusetts, or perhaps at a brownfield site in Anticostia.