Ned,
I've tried doing the arbitrator thing, and creationists tend to totally miss the point.
Every person who debates well is able to put themselves in their opponent's shoes. This is not so that you can agree with your opponent, but so that you can understand what he means by what he says, and then you can answer him effectively. It's important not just to rebut your opponent's arguments, but also to help steer his thinking, at least if you're going to convince him or any readers who might agree with him.
Every time I've tried to get a hard-headed creationist to look at what their opponent is saying through their opponent's eyes and understand the logic behind it, thus enabling him to answer that logic, I've gotten nowhere. They ignore my attempts to help them see every bit as much as they ignore their opponent's rebuttals.
So, my conclusion is that an arbitrator might be helpful for two people who are already somewhat reasonable, but who need a little help hearing each other, but for people like Buzsaw and the others mentioned, an arbitrator's assistance is as lost on them as the scientific method is.