I am always for a good ecumenical brawl, but I do not always have time.
I don’t think this idea agrees with the caucus philosophy. If someone on FR wants to agree with what you are refuting, why can’t he? If you are able to soundly refute it, why do you need a caucus protection?
For that to work you need a different designation, that encourages robust debate but discourages off topic posts.
As you know, typically when one subject is done, the side that is not satisfied finds another subject, to create an illusion of ongoing, even winning for them debate.
The article about Mary on the Cross is worth maybe a dozen posts. But do you have any doubt that on an open thread there will be hundreds of posts on some other subject, equally silly, equally requiring refutation?
On the other hand, if you post this in a caucus, make a dozen posts and the article is “refuted” you will not stop the anti-Catholic propagandist, who will say “that wasn’t an open thread”.
How can one limit debate to one topic, I don’t know. However, it would be a useful designation generally, because offtopic posts are detrimental to any debate.
Anyway, flag me if anything develops, I’ll try to pitch in.