Magento Categories are part of the
Mage_Catalog core extension which describes a category as an associative collection of products. To re-use Categories for anything other than Products may introduce undesired effects.
What I believe you're describing is CMS Hierarchies. Hierarchies were introduced in Magento Enterprise CMS+. According to the Magento Enterprise documentation:
The CMS Hierarchy feature is a categorization tool for CMS pages,
allowing users with no technical knowledge to create complex content
pages and sections of content such as Articles, Knowledge Base, and
more. The advantage to categorizing your CMS pages is that you will
then be able to display automatically generated menus and/or
pagination, to allow your customers to browse through the pages
The question is - how would we make this feature available to Community Edition? Your best bet is to install an extension. One that seems to fit the bill (though I've never used it):
Another option is to build it yourself - it could be quite simple. All you would need is a simple two-column join table that associates IDs of Hierarchy nodes to CMS page IDs. Another table would describe hierarchy node information - name, creation date, etc.
Two models and a collection would be all that is needed to get the information in and out of the db - a model to fetch and save information for the afforementioned hierarchy nodes themselves, and a model to fetch/save for the joins.
Displaying the information in Magento's admin section would be a deeper dive into how the
Mage_Adminhtml module works and includes setting up admin forms, routes, controllers, and grids.
Best of luck!