This is a nice proposal. I think the heart of the issue is the fact that the proposer of an idea or a suggestion gets a status boost if the idea is accepted. Thus, we experience a misalignment of incentives: ideally, I want my incentive structure to push me towards the truth, but actually I am pushed toward advocacy of ideas I proposed.

I would suggest some other roles:

The Fact Checker: this role seeks to ensure that the factual content of the proposed arguments are correct.

The Separator: the person in this role strives to separate terminal from instrumental values.

The Simplifier: the person seeks to simplify and refactor the arguments, making them as clean and direct as possible.

It would be fun to get a bunch of people, find some standard debating topic, assign roles, and see what kind of conclusions come out. In other words, to test the non-adversarial debating format and see what happens.