Look at it this way...
Bomb proof (sort of) new basement.
New electric and communications systems in the new East wing.
Stage with pulpit at one end with room for a big screen TV or movie screen.
Balcony area with 2nd pulpit at the end next to the central part of White House.
Room for a basketball court.
Press area on the open floor for what remains of the press, that can easily be herded in and out.
Kitchen area for catering.
Room for a fake grass golf putting green.
Room for a throne.
Ok, I couldn't resist that last one.
Regardless, the British Ambassador is not allowed to bring matches.