NewportGuy,
I don't believe that goal is attainable. The cost and logistics would make it prohibitive. Airlines like El Al, Royal Jordanian, among others, sustain the cost of multiple marshals per flight.

From what I have witnessed, there are typically FAMs on flights to "Category X" airports overseas: Frankfurt, London, Tel Aviv. I'm willing to bet that Amsterdam, Brussels, Madrid, Rome, and other UK destinations carry FAMs on each flight. I've flown the most from Frankfurt and Tel Aviv, and they've always been there. Not so obvious on Newark-Geneva.

Higher-risk airports elsewhere in the world seem likely. Caracas and Manila are both served by US carriers.

Within the US, I imagind that flights to and from Washington/National are the most heavily-guarded.