And Wikipedia is the content development area - that is a serious and very important thing. Without it there would be no content.
With an "official" cannibalization of Wikipedia arcticles for Nupedia articles there would be no content - people do not like it to write without being acknowledged. They get this acknowledment right now by supporting the free encyclopedia idea *directly*. I bet most of the contributors will have a very bad feeling about not doing the "final" thing any more, but being just the idiots who do all the work for some guys and girls at Nupedia who will be the "gods" which - at the end of the day - decide rather authorically what is good content and what is nonsens.
If you want the Wikipedia volunteers to keep volunteering, you must keep the "stable" versions under the Wikipedia label.
I say stable, not "approved". There could be a formalized, but still open process for building "stable" versions. You can start with an excellent article, put it into a sperate namespace or whatever, and than apply an important copyediting rule to it: "No new content may be added here, but content may be deleted". There are clever editors without degrees in the particular area that can do copyediting by throwing out everything that doesn't sound reasonable to them. Editors with a degree in the area are free to join in, of course and prevent the stable article from having wrong content by simply throwing it out! One can use the discussion pages for dabating which sentences will be thrown out and so on. If no new content may be added, there is a guarantee that this process will not work the same way like normal editing, where a lot of "arguing" takes place in the articles. If no new argument may be added, the article will shrink to the undisputed facts and gain quality.
After some time of copyediting there would be a freeze for the article and a vote, if it's ok to be declared "stable". Such a stable version could be merged back to the in-process-article, all the arguing there takes place again, and the cycle restarts.
Uli