Spilling out of my unblock-en-l experience...
It would be useful for block messages that blocked users receive to display some sort of block-unique ID number to the user (say, the ipb_id value), so that if they report it to admins (say, via unblock-en-l) we can go search on that key and not have to wallow around for a while figuring out what IP block or autoblock bit the person.
I was wandering around trying to understand the blocking code to suggest diffs, but it's given me a worse headache, so I'm just going to suggest it for now rather than trying to impliment...