Or perhaps the more people you kill in a single match, the more points you get?
Example
You kill 1 person with 100 points, and get 5.
You kill a second person with 100 points, and get 7.
You kill a third person with 100 points, and get 10.
You kill a fourth person with 100, and get 15.
Et cetera. Keep in mind that the current points system is based off of percentages, which is why I included how many points the theoretical person has.
However, the issue with this would be that people lose more points, faster. There was another thing but I forgot what it was while I was typing >_<
Another system would be that the later on in a game you kill someone, the more points you get, and the system also factors in what type of equipment they had when they died, or how many kills they had gotten that game. That would make dying more "expensive", and staying alive longer more valuable. In addition, people who want a lot of points would prefer longer games, as they gain more points that way, meaning that they also prefer maps that take longer to finish.