Here's my guess: If you propose this to Abdul Rauf, emphasizing, as you have in the past, the First Amendment rule that the government "shouldn't be in the business of picking" one religion over another, he will nonetheless refuse. He will offer all sorts of explanations but the truth, I suspect, is that he believes that Islam is not "one of the world's great religions" but rather the only true religion, that others are false and wicked. He will find it blasphemous that you want this center to give equal status to Christianity and Judaism. And he will see putting a church and synagogue on higher floors as symbolizing more than equality.
A bit of relevant history: Islam began, proudly, as a warriors' religion. Beginning in the 7th century, Islamic armies burst out of Arabia and conquered much of the known world. Among their practices: to raze the houses of worship of those they defeated and build mosques upon the ruins. This was a way of sending a message. These early Muslims were not just adept fighters - they also were skilled communicators.
The al-Aqsa Mosque in Jerusalem is built on the site where the First and Second Temples of the Jewish people once stood. However, some Muslims deny that there ever were Jewish houses of worship on that site. Why not ask Abdul Rauf his opinion? Might it influence your opinion of the Imam, should he claim that there were no Temples in Jerusalem prior to the Arab/Muslim conquest of that city?
Similarly, when Muslim armies conquered the ancient Christian capital of Constantinople, later to be re-named Istanbul, they turned the St. Sophia Basilica into a mosque.
As for the allusion to Cordoba: Proponents of this project say they mean to hearken back to a time when Muslims, Christians and Jews lived together in relative tranquility - under the rule of a Muslim caliph. But others believe it is intended to refer to the mosque built atop the remains of a church in Cordoba after Soldiers of Allah conquered Spain.
Prior to 9/11, most of us viewed the World Trade Center as simply an office building, a place where people worked hard day after day. But to the terrorists waging war against us, their supporters, enablers and apologists, the Twin Towers were a great Cathedral of Capitalism, a symbol of the power of what they call the "Zionist-Crusader" forces, against which they are waging what they call a jihad. That is what they believe they destroyed that day. To them, an Islamic center built on this site would commemorate their victory in what they regard as an historic battle.
Abdul Rauf may sincerely disapprove of the 9/11 attacks. But given his ties to groups linked with the Muslim Brotherhood -- former federal prosecutor Andrew McCarthy has reported on that -- there is reason for concern about what he actually does believe. To find out for certain, why not pose the questions I've suggested? See if you're satisfied with the answers you receive.
Mayor Bloomberg, you are the custodian of hallowed ground. We all want you to govern wisely on this sensitive issue. It is my sincere hope that, by writing you this letter, I may help you do that.