Michael's got it right, i.e. a rating system should be built around the CR. A separate package, perhaps, that exports an API that other packages could use to display ratings, offer links for users to rank content, etc?
He's also right that bboards in the ACES (which have a horrible threaded UI, about as bad as it gets) don't have a rating system of this sort.
The stuff you guys did for 3.2.x was based on the general links rating stuff, which I've worked with a little bit. It does seem that this might be a good place to begin.
