Not a bad idea! Maybe a Dual Site like Rush's with a Free Area as well as Premium Areas!
Here is my brainstorm.
The forum stays as is for the most part (donations optional). However, to post a vanity article or to post to a general discussion thread, one would have to pay a small subscription fee).
To do this, all that would be needed would be another "topic" or category which could be used to designate the "chat" style threads (The Guild, ATRW, The Smoker's Lounge, FReepoles, etc), and have an access level or list inplemented in the software to limit access to that category to only donors. Since these threads have no copywrite protections, there should be no fair use concerns.
The vanities would not need a special category- just a warning that vanities are only to be posted by paying customers and donors when a person tries to post an article, and then the moderators could pull those which are vanities posted by non-paying types (and I am not suggesting the mods get access to who has been donating how much. All that would need to be visible to them is a yes/no flag for the article's poster).
In each case, we would be charging for the content which is distinctly separate from the published, copywrited articles we debate.