Idea:
Substract points from player score which given players "caused" the other team.
Example:
If I have, say, 57 Points and the other team freezes me (-1) and kills me (-5) I have 51 points.
At the end of the round every player that has a score > 0 was useful to his team (team switching ignored..)
Team score and thus round length should stay unaffected, the purpose of this feature would be to rank players more realistically.