What a great idea! Structure the debate and build in some obstacles to crazies.
Unfortunately, the power structure does not seem to land at "Who has the better argument?" But at "What does the online audience think is the better argument?" We are back to rewarding the conventional wisdom.
However, it is probably a step up from our current debate even if it has flaws, and bsking has convinced me that this is also a worthy goal, even if it falls short of getting a grip on the truth. There is a site LessWrong that takes this approach, and I sort of like it. However, it has an air of being inoculated against certain ideas because it has deeply hidden assumptions that the contributors share and cannot question. Example: That the Enlightenment got almost everything right as a foundation, it just hasn't been tried properly yet. Sigh.
I give both sites three stars out of five.