There are many forms the target nymber approach could take. For example, the critical increment number could be used to determine when a blow that only delivers hits results from attack roll. A 95(20) would be a weak knife, and hits only would occur on a 75-94. Weapons could be rated for hits, in this case say 3, plus St mod. Each crit stage would increase hits x1. So...
75-94= 3hits+St mod
95-115= 6hits +St mod + A crit
etc.
Armor could have a stat that negates some hits. Whatever. Game designer and play testing would be needed, but the variability of weapons would be tremendous, and I am far more concerned with playability and fun that realism. Also, A simple core series of mechanics with tons of options that CAN be adopted if desired I believe would be the best approach. Simple as the core, add complexity in the optional section of Arms law, which would be MOST of such an arms law, as the base mechanics will take up very little space.
TMWTD has a very neat mechanic to figure critical type. Based on the AT attacked, the last number of the attack roll determines what type of crit is scored. So an attack roll against SL with a broad sword will be slash on 1-7, puncture on 8-9 and crush on 0. Likewise, an attack against plate would be puncture on 1-6 and krush on 7-0. This info is easily listed with weapon description or armor description.