Imagine that one person has decided to harm another, and the only thing they have is a hefty sewing neeedle the length of a hand. Now, you might say “that’s a bad weapon, it should deal 1d2 or even 1 damage!”. You might be right. But I’m pretty sure you wouldn’t want to be stabbed full force with a 18 cm (7 in) metal spike. Being a straight bit of metal, it’s likely that upon encountering any properly hard object, the needle will slide through the user’s hand, as their grip friction is weaker than the surface’s resistance. So, if you stab someone in the abdomen, that’s a comparatively soft bit and if the needle pierces something important then the stabbed person is in trouble. If you stab someone in the thigh, it likely wouldn’t be fatal (barring infection or ruptured major blood vessels). If you stabbed someone in the forehead… I don’t think it’d go through the skull.
Piercing weapons are highly dependant on the location of the hit. Contrast that to a saber: while there’s still a difference between slashing someone across the chest and across the belly, it’s much smaller as cutting weapons rely on making long but comparatively shallow wounds. You’ll bleed a lot if someone cuts open both your pectoral muscles, just as you will bleed a lot if someone cuts open your stomach.
As you die no matter if it’s a dagger or a zweihänder that pierces your heart, the biggest advantage big weapons have over small weapons is the ability to deal heavy damage despite the hit location rather than a huge flat damage bonus. Any decent weapon can kill a man in one blow (though, not necessarily instantly).
This made me remember a damage system a scribbled down in passing once, and I’m not sure I ever posted it:
You roll two damage dice, one for weapon size/power, and one for the hit location, and used the better one. Both the power- and location die went from 1d4 to 1d12.
As the hit location improves, the difference in damage lessens (though it’s always present). And the damage difference between a d4 and a d12 weapon at 1d4 hit location (2.16 times) is actually less than the difference between a d4 and a d12 weapon in a vacuum (2.6 times), which might actually be desirable? Also, I just realized that I still have excel 2003 on my desktop computer. Huh.
It’s not that advanced, but it kind of captured that idea. The problem is obviously that you first have to roll to-hit, calculate hit location, and then roll that damage together with your regular damage. Nowadays I’m leaning towards HP/stamina as a buffer and then rolling meaty hits whenever that buffer runs out. It might take the better of both worlds? It gets the quickness of HP but the interesting results of a wound system.
Now… calculating the kinetic energy of a blow is relatively simple, but calculating the damage value of a ruptured spleen vs. a broken arm is tricky to say the least. That would likely take a lot of time and effort, but it might be worth a shot.