I was impressed with the Privacy Options offered at wordpress.com and their ability to make private blogs. From the looks of it they simply extend the Privacy Options page to have it manage users in the Subscriber role, then hide that role on the User List by Role page. When activated, users without Read permissions are always redirected to the login page.
They seem to prefer to make hacks over plugins, so I decided to reverse-engineer their hack. I've been able to do it as a plugin but I currently need to enter two lines of code in options.php and options-head.php. Would it be possible to add an action in two spots so my code can be a 100% plug-in? How would I go about requesting that? Basically I just need a way to intercept the option setting process and add a second status message, and with that I can 100% replicate their functionality with my plugin (and with no 35 member limit!).
I'm putting the finishes touches on my plugin now and would be happy to release it when it's ready. One question, what's the best way to fetch a list of all users in a specific role?