@julian Do you see an easy/nice way how to solve this problem?
A not very practical way would be to create a group for each category. Unless you write a plugin or script to ease the pain of management it will be headache inducing.
I was wondering what the recommended practice for Auto Login was. I have a "members only" area of my website, and from there I would like them to be able to access a forum, but ideally they would be signed in. The current solution isn't OAuth based, so I'm not sure if that's the best route to go down - or if there might be a hackier alternative?