They could only ever work if two moderators were used and one was a lib and the order was an Alex Jones or a Rush and the questions were unrestricted.
Also Party ringers need to be excluded from the audience and none of those idiotic townhall style debates.
I would like more of a discussion around a table situation, but that would have to with only 2 or 3 participants to make it workable, I suspect. And the moderator should be a strict, astute someone they all respect, preferably a non-media person. I know, seems very improbable.