Each unit gains veteran levels from 1 to 5 which provide "buffs" like extra HPs or self regeneration for achieving a predefined set number of kills ranging anywhere from 10 to 2000.
This mod allows your units to achieve a level of veteran's for each kill it gets.
No other balancing is done, so this makes games a little interesting.
My second mod. This one is a little more advanced than my first because it takes advantage of the hook directory.
Just unzip to your mods folder and select it from within the game.