I guess it's quite a wild thought, but could it be hard to code some sort of rewards for kill streaks?;)
I don't mean attack helicopters or anything, but for example, a person who killed like 5 in a row would radiate glowing or will receive a timed banner noticeable by both teams.
Such people will receive more attention from the opposite team, therefor making it harder for them to get more kills in one life.
I think it can balance the skill difference a bit;).