From what I can see perks are a direct result of the skill required to get a kill, multiplied by risk of death.
Field and ships guns take very little if any skill, and no risk. Someone kills the gun emplacement you don't even get a death, just back to the tower.
If and only if, HT puts your icon over a gun, so a player flying by can see which one to kill first.
If and only if, that gun is then destroyed, and the player gets a death.
Then and only then should people get perks for kills in that gun.
You want perks, jump in a plane or tank, and earn em.