Level two charging seems different than Supercharging. You charge full speed almost until the car is full on Level two, but the supercharger spends 15 minutes recharging the bottom of the battery and an hour charging the top. When I travel I rarely spend more than 20 minutes charging. Perhaps that would be a good compromise for the superchargers. If no one is waiting you can charge to the top. Otherwise, it only charges to 70% which is more than enough for you to get to another Supercharger if you are traveling, or drive for many days if you are local, giving you time to return when there are fewer people waiting.
-Randy