I think I've covered all the cyclic dependencies you've listed in previous comments, but here's just a quick rundown:
- This handles routing back to a default page if the model does not exist.  Since Marionette separates the router and controller, the only options are this, or trying to force the page to load a specific url (not desirable).
- All content models (and their inheritables), including book, container, and module, are explained in more detail in the discussion under ```scripts/models/content/module.coffee```.