No mention of assessments
In the proposal there is no mention of assessment or feedback on progress which I consider essential for learning (rather than just informing). One technique I use in my online tutorials is to have assessments attached to each concept (single page). The results of these assessments are used to provide guidance through the tutorials using a fairly simple but affective probabilistic network. This could I think be integrated into what you propose. Even better have different prople write the assessments than the provide the information - then a measure of how effective a particular tutorial is can be measured by the average students performance on the assessment. You could perhaps even use the extreme programming idiom - write the tests first and then have people write the tutorials to enable students to meet the measured perfromance criteria.
A second point I would take issue with is the use of a strictly heirarchical approach - not all information can be represented in this way. Additionally you may wish to refer to the same concept/page in several different tutorials. Again I have solved this by treating the tutorials as simply a collection but allowing concepts to specify n - the same concept can then be used in differing heriarchies.
The connexions project uses topical modules that each stand alone, but also can be organized into "courses." All the content is on the Creative Commons licenses.
From the front page:
The Connexions Project is a collaborative, community-driven approach to authoring, teaching, and learning that seeks to provide a cohesive body of high-quality educational content to anyone in the world, for free. The project involves two basic, interrelated components: (1) a Content Commons of collaboratively developed, freely-available material that can be modified for any purpose, and (2) open-source software tools to help students, instructors and authors manage the information assets in the Content Commons. Connexions provides an open, standards-based approach for sharing and advancing knowledge to benefit the global educational community.
Check out the "explore repository" at the bottom of the page to get a feel for the modules.