Don't allow residential development within the new capital. Keep the residential developments away from the government structures to further security.That was one of the things we'd thought about as well. No one should live in the new capital except the President and his immediate family, the Marines currently billeted at 8th and I, and the Army's Old Guard.
Nothing but pedestrian traffic allowed on the streets. We'd thought of laying out the pattern as a sort of bullseye shape - concentric rings of broad pedestrian avenues with a N-S, an E-W, a NW-SE, and a NE-SW avenue intersecting. At the center would be the White House, the Supreme Court, and the Capitol Building. Behind each one would be the various governmental agencies. The outermost ring would be where all the monuments, the Smithsonian, the Library of Congress, etc., would be. It's a lot of fun just to try to lay it out.
I'd bet we could come up with some grand plans if everyone could work together on this.
I'd leave all our monuments and museums where they are now. The present federal buildings should all become historical sites under the control of the Parks Department or the Smithsonian. The influx of tourism to visit the great halls of Congress, the White House, and the many other buildings would probably raise enough revenue to maintain all these buildings and cover the expense of the entire department nationwide.
I figure with 10 square miles, and no residential housing, a new city would have ample space to physically separate the three branches of government. That would further secure our government from being destroyed by a single strike.
Thanks for keeping this thought alive. I'll write more to you later.