Unless you self-publish, only the publisher gets sales numbers from Amazon. Amazon rank is indicative of sales in a general way, but not specific. If your ranking climbs, you know that's because of a sales increase, but a rise of several thousand in rank may only translate to a couple of books sold. I don't think your idea is workable, Sol. And I don't really see the point, as it would create an irrelevant competition among TNBW published authors who write in various genres and use various promotion discounts.
I agree with the irrelevant competition aspect. When I do a promotion, my ranking will shoot up by tens of thousands. And then it quickly goes back down. And what would be tracked? The overall Amazon ranking? The genre specific? And which genre, since Amazon allows up to three? Us authors are keeping track of our sales based on the bottom line, royalty payments. No need for TNBW to do it.