Hm, well I would have a use for something like this. I'd love to be able to manipulate hashes like this through a standardized API. In fact, I already use Tie::Hash::Sorted for some things.

In terms of suggestions... why not make your module a wrapper-replacement for Tie::Hash::Sorted? Import all of its methods, and extend it with your ranking items (and some of the stuff you suggested in your new features list. Call the new module Tie::Hash::Sorted::Rank or something.

Most importantly, keep the interface consistent with Tie::Hash::Sorted so that new users of your module will not need to relearn anything.