What we should do to "terrorproof" the new WTC

This is an idea I had a while back which I posted here on Fark:

If we give the top third of the building [the Freedom Tower] to the United Nations, the current location can go back to NYC, the UN would get updated facilities (which they have complained about fairly recently), and diplomats would have their attention concentrated on the problem of terrorism. It's a win-win-win situation.

Later on, I went into more detail on one reason:

The United Nations currently wants to complete overhaul its current headquaters, to the tune of a $1.2-billion interest-free loan, and an additional $650 million spent on a 35-story building to house UN employees during the renovation as well as a 100,000-square-foot park. The total bill may be as much as $2.5 billion, with U.S. taxpayers expected to foot at least a fifth of that. For the same amount of money, they could get a penthouse view of New York with state-of-the-art facilities. One would wonder why they wouldn't want to do so.

Other than fear, of course, which I'm told concentrates one's attention quite effectively.
*******

/Posting here because I'll lose the Fark thread otherwise :)