Just an idea...

Medieval 2 Total War, has a small short coming on the unit attack stats. So when we do a list of weapons and their attack value to suit the game, we only look one number. Where as it should be two numbers: 1. Attack Rating of the weapon (Damage) and 2. Attack rating of the man wielding the weapon (Skill). So when counting/estimating these attack values, it could be better that we make exell sheet where you have weapons attack values and the skill level of the man count seperately and then together. Then just put the counted value there. There is similar thing in defence ratings of M2TW. Theres skill, armor and shield values seperately.

Quick example:
Knife: 1
Sword: 3
Long Sword 5

Peasant: 1
Militia: 3
Veteran 5

So now having veteran wielding sword vs peasant wielding long sword = 5+3 vs 1+5 = the veteran would win by two points due experience.
So then having militia with knife vs peasant with long sword = 3+1 vs 1+5 = the peasant would win by 2 points due better gear.

(Example is just random numbers. But made it quick to clarify the idea.)

Same can be used with the crossbows and ranged weapons... in a hands of unskilled peasant they are not that effective. Chevrons (experience) changes it tought.