I have some ideas that I've toyed around with in my mind for awhile and just now decided to throw them out to you all.
1.) Kill assists. PB2 will have a kill assist system. Each kill assist will count as .50 towards your overall KD/R. Kill assists may be defined as a player having dealt 50 or more damage to an enemy and it would only count for the next 60 seconds since dealing that blow to the enemy.
2.A.) Kill streaks. Maybe a point multiplier for kill streaks or something.
2.B.) Kill streak ended bonus points. A player will be rewarded for putting an end to a player's kill streak.
3.) Comeback bonus. Players getting trashed and end up getting a kill can be rewarded. A little incentive to keep them going, rather than them just rage quitting.