Hello paolo oprandi, 5 years after, I agree 1000% with you .
Your contribution/idea/point of view is exactly what i'm planning to do: All courses should be opened to guest (+google) and then Permit/Prohibit "stuffs" for each Role at each level.
Im not a Moodle core developper, neither teacher but i've been playing around Moodle for a long time and TODAY my vision of a School Portal running under Open Source Application is to be completely Open (lol).
(i would like to contribute with my visions, but my english is too poor as the French Community resources )
Will share the results (portal design + navigation design) very soon.