You can restrict access to the web inbox or the personal call routing rules via COS settings but you can't pull specific items out of the user's PCA pages.
You can assign users to a COS that has restriction tables that don't allow any numbers - this would deny them the ability to set any notification devices at all - they can see them but wont be able to do anything with the phone based devices - this is fairly common.
the ability to be able to customize the PCA pages to installation taste has been bounced around but so far as I know is not on any committed road map. It's less than trvial given the dynamic nature of the web interfaces (i.e. built off the data dictionary on the fly so new items get added easily). As ever it's best to make sure your account team logs a PERs request so the account team knows sites are wanting this functionality.
