If some articles are moved to a "safe haven" -- whether that be "ExpertWikipedia", "Nupedia" or just some [[protected: namepsace of wikipedia -- they should not be editable there. That's only going to lead to two concurrent versions of an article, which someone is going to have to muck around merging in the future.
The multi-tiered system with voting sounds horribly complicated.
The basic idea, as I see it, is for one particular revision of a page to be protected & marked out as being "good", in the event that vandalism or general rubbish occurs. It wouldn't be hard for a page to have a "view last approved revision" link on it.