What you said makes me wonder about a totally different way of using a metric of how likely the person is to win a given match.
That is, perhaps the system could be engineered to maintain a more even win/loss ratio so that people don't go on super-long win (or loss) streaks in general by adjusting who they get matched with.
It probably wouldn't work that well towards the edges, but around the middle it might work well enough.
This has what dota 2 does. Every win / loss is worth the same points, the games are extremely close in terms of player rank, so and it's a team game so you get more variance than just your individual skill. Players eventually settle close to 50 percent win rate
That is, perhaps the system could be engineered to maintain a more even win/loss ratio so that people don't go on super-long win (or loss) streaks in general by adjusting who they get matched with.
It probably wouldn't work that well towards the edges, but around the middle it might work well enough.