Let me explain.
Explanation received and understood, clearly illustrated by your example.
I don't disagree with your objectives but as it is my nature to contrary.....
While using median instead of basic average would benefit a seller who is only marginally gone to the "bad" it would also benefit a number of poor sellers who don't deserve the help.
From various posts by pinks, announcements and interviews with eBay execs I am getting the impression that while the basic policies are here to stay there will be a close examination of the results and ongoing tweaking of the parameters are a foregone conclusion.
One thing for sure, when you are dealing with hundreds of thousands of active sellers operating under a myriad of business models it's very difficult to set the terms of any policy so that even a majority of sellers are treated equally. I'm afraid there will always be some sellers getting the short end of the stick some some degree.

"What else could I do? I had no trade so I became a peddler" - Lazarus Greenberg 1915
- answering Trolls is voluntary, my policy is not to participate.