A user experience for creating menus in a CMS is not a concept related to OOP, users of a web site have no idea about OOP. Using web site software as an end user is not related to programming. So quoting some Grady Booch OOP book to convince me its important to make mojoportal work like joomla doesn't sway me. Its not a related concept.
mojoPortal has a site hierarchy reflected in the site map and this site hierarchy is easy to re-arrange as needed already.
Structuring of menus is a skinning/UI design concept and a variety of of configurations are demonstrated in our many included skins.
If you are a developer you can build custom features using the ASP.NET treeview control without using a sitemap by programmatic adding the nodes.
I have no magic solution where users can make arbitrary treeviews.
Once I implement a core feature for categories I may use that in the links module to make a treeview of links grouped by categories. But to me that is a very different thing than a menu for site pages.