You go out of town for a day and when you come back the Mayor is proposing to move City Hall to the Seaport District. The responses have ranged from the predictable (City Hall is ugly and must go) to the conspiratorial (Menino is on the take from developers) to the practical (I don't want to have to take the Silver Line to the waterfront).
Jay Fitzgerald offers the most rational approach, which is to renovate the current City Hall, a view echoed by Robert Campbell in the Globe today. More support for City Hall can be found at Universal Hub.
I would take the support for the current City Hall one step further and build a City Hall annex on the Congress Street side of City Hall Plaza, stretching back into City Hall Plaza. This annex would not only handle most of the face to face transactions people have with the City of Boston (one of the main complaints of visitors is that the current City Hall is depressing) but could also provide space for a new museum of Boston history, with an entry for a National Park Service visitor center at the ground level on Congress Street.
Reconfiguring the walking paths through City Hall Plaza would also make the route to the North End clearer for those coming from Boston Common/Beacon Hill, perhaps by taking cues from the original street layout which ran through Scollay Square before redevelopment. The idea is that a museum/visitor center would act as a funnel, collecting pedestrian traffic. Of course, the Congress Street issue would have to be addressed, but that's just icing on the cake, right?
While the proposal to relocate City Hall to the Seaport District and sell the present location for development has the advantage of helping to pay for a large portion (all?) of the new building, there are ways of financing renovations and an annex. I would open the Cambridge Street side of the plaza to residential development (akin to the housing which skirts the Saltonstall Building/100 Cambridge Street scroll down the linked page for a photo) or low rise commercial development to provide a better edge to City Hall Plaza and perhaps a taller office building at the corner across from the JFK Federal Building, although proposals for that corner have proved problematic in the past.
I do understand the Mayor's desire for a new city hall--the Greater London Authority's City Hall is a beautiful addition to the Thames waterfront, and there is no reason to doubt that something equally striking could be done here in Boston, but the location in the Seaport District doesn't serve the people well nor is it conducive to iconic architecture, since the views of the new building would be limited. I took the Silver Line from Logan to South Station yesterday and I don't believe the Silver Line is capable of handling the increased transportation demand. I would have liked to have seen light rail running along the Rose Kennedy Greenway (essentially duplicating parts of the old Atlantic Avenue elevated) from South Station to the North Station area, with a spur line running over the Northern Avenue bridge to the Seaport. This won't happen of course, but a single Silver Line station serving as the only connection for a new city hall to the larger T system is completely impractical. There are also complications from height restrictions and use restrictions for the proposed location, although one would suppose a highly localized overlay district would be easy to obtain.