building on the current system of wearable carriers and webbing, create a optional modual that allows body armor such as plate carriers (but not webbing or similar) to stop small caliber rounds such as pistol rounds and lower caliber rounds such as 5.56, but for calibers with larger mass such as 7.62 and 6.5 cause the character to be incapacitated for a shot period of time (say 2-3 seconds), like as if they were hit by a bike a low speed, while 3-4 rounds would penetrate.
and for higher caliber mass/velocity such as 12.7mm rounds allow the round to penetrate the body armor and kill.