I'd be really interested to know what kind of arguments actually work for the AI. I find it hard to understand why anyway would believe they'd be an effective gatekeeper.

Could you maybe set it up so we get some transcripts or aftermath talk, maybe anonymous if necessary? (You seem to have enough volunteers to run multiple rounds and so there'd be plausible deniability.) If not, I'd like to volunteer as a judge (and would keep quiet afterwards), just so I can see it in action.

(I'd volunteer as an AI, but I don't trust my rhetorical skills enough to actually convince someone.)