I'm working on a project to combine other access control attributes, such as rate limiting and user privacy lists (white & black-lists), based on Groups, Users

I'm working on a project to combine other access control attributes, such as rate limiting and user privacy lists (white & black-lists), based on Groups, Users & Nodes. Reverse indexing would be very hard e.g. for an ever-growing threaded discussion where participants may be of different groups, and where sub-thread access would need to be moderated (moving posts, restricting access to specific people etc.)