An option for events to be "private". I.e. they don't show up on any events pages, they can't be accessed without the URL being sent to them, etc.
We'd use them for private donor events we host so that we can still give a web address with details, as well as an ability to track RSVPs and donations through codes, etc. But they could only be accessed by those we explicitly invite (through e-mail blasts, or private e-mails from hosts, posted invitations etc.).
Liam, to accomplish most of what you want now, you can use "membership" page-level control for the folks you want to be able to attend. You can also create a calendar for exclusive events that are not included on your general events listings - anyone not invited with a link would be unlikely to find them.