Despite not having regular status, I don't think this is a good idea. I get the impression that you and the others involved in the decision probably have a slightly different understanding regarding elitist and egalitarian approaches than I do. It's a bit like hearing libertarians talking about the virtues of liberty. I will watch BB BBS, and see what happens. My best guess is that BB is big enough to attract enough people for a message board, but the community might get a higher turnover.
Even from without the in-group of regulars, this feels like you are actually harming your own intentions.
Regarding your regrets, I think if you want to see the regular/lounge past as a fault, then it's not yours. Discourse comes from the StackExchange part of the web - and this is exactly what you get if you use discourse. Badges, merits, etc., pp.
Disclaimer: I read your post and more than 100 reactions. I am too tired at the moment to read the other hundreds, so please don't be mad if I am not up to date with all of the discussion.