Currently the system allows restriction (blacklist) on a page by page basis. What is needed for large spaces is the ability to grant access (whitelist) a page for specific users or groups.
In our instance we have several massive spaces representing projects with various groups who need various levels of access. For groups that need to see "most" of a space, it is manageable to blacklist/restrict the pages a group should not see. However, when a group needs access to a handful or only one page in a space, it is completely unsustainable to restrict and maintain restrictions on 1000s of pages to do so, and much more feasible if there was a system to greenlight/whitelist a page for a user/group of users.