I had a kung fu instructor who used "play" to teach principles. Uke would go down on all fours and Nage would try and flip them on to their backs. Uke would resist for a while until "nage" got it. Non-competitive and totally in fun so uke could just turtle up if they thought nage was a bit slow.
Following the side diversion re: uke and nage. I always understood uke was the one who recieved the final technique ie ended up on the ground. Is this definition only relevant to formal "kata"/technique training?
I've been thinking lately we should all spend more time on "drills" like you describe.