So you know, I wasn't volunteering to write the module per se. I was commenting on the possibility and ease of doing this specific task and noting caveats that may come with it. However, since it's a simple module I may get around to it or I may not (time restrictions).
After some thought, you may be able to use extban ~a:account. I'm not sure but ~R:nick certainly will work.
To be honest, this is one of those modules that would be perfect for someone wanting to learn. *hint* *hint*