@Pandry Interesting. I don’t know the code base either, but my intuition doesn’t necessarily agree with yours. 
If they don’t have the concept/code for “pinning” a page at all, i.e. a sidebar, then they at least have to create that. The data model for page linking already exists. Visualizing that may or may not be fairly trivial.
In your concept would the tree have to be created and maintained manually by the user? If not, aren’t you describing basically the same thing, just using some existing components/capabilities (links and blocks and pages)? If it uses existing capability but is auto-generated, would it also be user editable? If yes, what would happen to the auto-generation process if a user edits it?