This is why the Planet Money approach works so well. Rather then an AMA, perhaps there should be two guest economists, and a political topic is chosen to be discussed. The discussion could focus on the economics, which would appeal to the technical side of HN and remove a lot of the typical emotional appeal. I would also propose that for those topics, voting be disabled for the guests replies. The purpose is to show both sides a discussion, and voting typically turns populist on political discussions. (I know about false equivalency fallacy, but I think for politics it is important both sides have a voice)

That being said, I wouldn't be surprised if there is already a HN economical equivalent website somewhere, just its outside our tech bubble so we (I at least), have not stumbled across it.