As more direct answer to hitech, it is not about the score. If you take scoring out and just focus on the human aspect of it. Manned guns are currently a one sided affair, a low risk, low investment one at that.
Make it even, either by awarding kills to all or none.
Your game do what ya want, I'll still play. I see the value for having manned guns, my dad, Would love to have something he could watch tv and wait for the HITECH call to arms and jump instantly in the fight kill a few people and resume tv watching. His satellite internet is a nonstarter tho.