I'll put this as gently as possible....
No. Not an *easy* way. It would take a fair amount of calls and lots of parsing / sorting data to arrive at what you want.
In regards to getting ranking stats for a specific date, we dont offer that at this present time. However, you can get really tricky / clever with User Reports in metrics, to give you historical snapshots of user's activity levels during specific dates, but those reports will automatically expose the user's current rank (rather than their historical rank), even when outputting historical data.
Sorry, I dont have a more positive response to your question(s). :(
Still would love to be able to query on this, I tried this:
http://forums.comcast.com/restapi/vc/ranks/list/users/count
And got:
