I must admit, this type of thing as you and dflock have described has always been in the back of my mind. I kept tell the thoughts to go away because thats a pretty big undertaking. Fortunately, I actually have experience building customer facing rule engines.
This is dangerously tempting to work on. Should I go for it? Perhaps I would need to provide both methods of awarding badges. I dont see StackOverflow.com wanting to re-implement their badge system rules in the KaBadge system.