I would like to know if it's possible to hide the "Who can edit this inside the CMS" section from the "Access" tab.
My idea was to hide it from all users except for the Administrators ("full administrative rights" permission).
One more thing, is it possible to establish that a group only has access to a especific pagetype in the sitetree? (I think it's almost impossible).
for hiding the access tab, you could subclass CMSMain (e.g. with "MyCMSMain"), override getCMSFields and remove the field manually if necessary. to have your subclass of CMSMain used instead, you have to add the following director rule to your _config.php