Every moderator is biased to certain degree so trying to find unbiased one to moderate debate is pointless. Instead they should bring one with obvious conservative bias (Hannity/Gutfeld) and one with obvious liberal bias (Maddow/Cooper).
This way both sides will be challenged every time they want to avoid to answer a question.
My idea, debates should have two openly biased moderators picked by each side that rotate between asking questions for their team and the opposition. Each candidate would get asked hard questions and also get a chance to highlight accomplishments