Who wouldn't want to see Tyler Cowen publicly debate Robin Hanson? Well, aside from the masses? I think they'd both be willing, if they could only pinpoint a good topic. A while back they had an extended blog dialogue (see here, here, and here); can you extract a resolution from it?
Personally, the bottom line of Tyler's latest post reminds me of a debate topic that someone suggested after a recent seminar: "Few major changes in the policies of modern democracies are desirable." Depending on when you ask him, Tyler might deny that he believes this, but in his heart, he does. And no matter when you ask Robin, he'll be ready to argue the contrary.
Other topic suggestions? If Tyler and Robin wind up using your novel suggestion, lunch is on me.