I have an idea, how would you feel if head shot's only did 1.5x damage but if you manage to get a headshot there could be a chance of drops instead, ie killing a soldier via head-shots would have a 10% chance to drop 10 rifle ammo / 1-2 health pills / or a couple armour shards

However killing a boss tier enemy lets say khnum could reward you with a higher pool of drops,with a 20-33% chance of dropping one of the following? 10-25 health bonus / 10-25 armour? 1-2 rocket ammo, 10 laser ammo, or what ever you used to get the head shot kill

although doing this would give the game a more arcade like vibe to it but then again we already have a basic perk that pretty much does the same thing but for any kind of kill