Seen as all the player models are made of separate voxels anyway, why not allow actual player model damage. ie. when a bullet hits an enemy, there actually will be visible damage to the model like a hole through the chest or head...
I would say the damage ratio would be like this:
Shotgun: each PELLET (not shell) penetrates one voxel deep and the adjacent voxels on the model would change to a pink-red colour showing the wound clearly... (thus the closer you are the deeper the hole due to the concentration of pellets)
SMG: almost the same as a shotgun pellet, however the bullet penetrates two voxels deep
Rifle: Same again, however a rifle shot has no maximum penetration thus the bullet passes straight through the body. (May Create the hole to 3X3 voxels, however this is up for debate.)
ADDITIONALLY: Limbs could work in the same way structures work on terrain, if there are no adjacent voxels keeping the structure connected to the ground it falls down, in this case say you were shot in the upper arm with a rifle, blowing the whole arm off... the rest of the arm would fall away!
Optionally:
I also had the thought (plus some of your comments ;) ) that having your arm blown off or leg blown off would OBVIOUSLY hinder your movement capability so (Just an idea hehe so shoot it down as much as you want)
1. that you would go down to the ground... with camera view the same as you would if you were dead (should you be able to shoot whilst down or just be injured?) while other players could come to your aid with adrenaline or the likes. this shot wouldn't heal you, but allow you to make Your way back to the closest Command Post.
else
2. rather then going down, Severely slowing the player until they reach a command post...
personally id rather not add either of these to the game (Gets a bit complicated :S) but then again maybe it would be nice haha if I had to choose i would probably prefer option 1. since it will promote team work in game...
Obviously, not all players will find this option enjoyable (to gory or what ever) so thats why i thought it would work well as an option in the config file.
Thanks for reading, tell us what you think :D
[EDIT] spelling errors corrected, added injury disadvantage