In Wikipedia this is handled by categories. That's how it's been handled in VaultWiki too since its inception. I don't see that a "cleanup" special page would make this process any easier. A number of special pages can already be used as indicators of cleanup with finer granularity than a generic cleanup page might.
One thing I do believe is missing is better explanations of each special page. That and special pages have historically been sort of an after-thought and need more attention in general when it comes to features and usability. In this case, though, I don't believe a new special page is needed.