Jd Smith1
Hero
I guess one obvious result of implementing a system like you have in mind would be opening up the idea of 'called shots' where an attack is made against a specific part of the body e.g. "I go for his weapon hand" or "I try to take her knees out" - something D&D has never supported despite a few vague wave-at-its in the distant past.
Long ago I tried a simplistic called-shot system in a 1e-like game. It lasted maybe two sessions. Complete mess. I learned that to do it right required, in effect, assigning separate AC values and hit point numbers to each body part; and life is too short for that.![]()
I've never been a supporter of called shots. After over thirty years in law enforcement plus military service, and extensive work with various melee weapon systems as a hobby, I don't really see it as a viable option (except perhaps in dealing with approaching zombies, where the actor is unhindered by enemy action).
Highly-trained individuals can, as history shows us, make head shots under combat conditions, but otherwise, I'm not inclined to allow it.
I've always handled head shots in game by assigning a hefty penalty which ensures that only high level types can consistently pull it off, which jibes with reality.