interesting idea. From my own experience as a martial artist, I'm a guy who's better than somebody who sucks at any given weapon (meaning, you pick a weapon, and give it to me, and a guy who sucks at that weapon, and I will kill that guy with that weapon).
That's not saying much, other than I have a decent understanding of weapons in general, and a success rate that is better than bad.
Here's what I know:
I can kill a person with any weapon, however, the choice of weapon may make that task easier or harder.
Imagine you have 100 HP. I can possibly hit you for 100 damage in that fight. With a knife, it's kind of harder, with a sword, it's pretty easy. With a pistol, it's no contest, with 5 rounds in 10 seconds, 2-3 will land in the killzone at 45 feet.
Reach is a key factor to lethality. If my weapon is longer than yours, I have an easier time to kill you. If it is shorter, it is harder to kill you before you kill me. It is primarily because I am safer from you hitting me, before I hit you.
Shields make it really hard to hit somebody with a melee attack. As in I almost never get hit, when I spar with a shield, compared to the shieldless guy I am fighting. It is generally really easy
Armor negates or lessons weapon impact. Light weapons, it pretty much negates a hit, heavier weapons (bigger swords become blunt attacks, and blunt attacks still hurt, just less).
Ranged weapons (guns, arrows) tend to penetrate armor. From a functional standpoint, I'd say they are close to the same thing, barring armor that's designed to block exactly that (like kevlar vests). Again, such wounds range from grazing to lethal, really just as a function of where I hit. And a decently skilled person, with time to aim, will likely score a lethal shot.
Mostly the keys to not getting hit are blocking, dodging, having longer reach which causes the other person to be more cautious. That's all obvious, but the reality is, getting hit is a serious buzzkill to continued fighting. this is why animals don't fight to the death. it hurts, and your odds of winning go down a lot, as you are slower, and encumbered with a wounded part that must be protected.
Strength plays a role, as a stronger guy hits harder, causing the target to be more cautious, as well as making them reel from any given blow.
Size also matters. Larger people have more reach, and reach is king. Barring extremely obese people, being bigger does not mean slower. Football players have pretty much proven that on the Jousting League stuff that goes on today. The only advantage a smaller person has is their training, if the bigger opponent is less skilled.
Every melee ends up on the ground very quickly. be it 2 drunks in a bar trading punches, or 2 scotsmen with claymores. They will trade one or two blows, and if that doesn't end it, one will step in, and the fight will turn to grappling on the ground.
That's a whole lot of factoids. I think they can be used to define game mechanics. Just some rough ideas here:
damage on a hit is 1-100% of the targets HP (using % to reflect that I can kill you or graze you). The possibility of 100% needs to exist regardless of circumstance (barring really extreme exceptions).
The probability of getting higher damage is based on difference in skill, reach of opposing weapons, luck, armor, dodging/blocking ability. The more factors in my favor, the more likely I can get a 100% damage hit. The less in my favor, then the more super lucky I need to be to get that lethal hit in.
I'd be curious what kinds of designs come out of that.