What about a system where dropping constantly causes you to be paired with other droppers? So if you drop like 10 team games in a row, most of your future games will be with people with a similar tendency. If you haven't dropped in a while you eventually move out of this pool.
+1 I like that idea. Match droppers against each other and they can drop and enjoy unfulfilling games. AFAIK, they are tracking the number of disputes but I'm not sure if dropping a game via '/leave' or "Quit Game" counts as a dispute. At the very least, it won't ruin the experience for those who actually want to play.
On the other hand though, there are people who never want to surrender even you've lost 90% of the map, outmatched, and opponents are in their base. What to do about these guys?