I like it. That sounds alot like Diablo 2, except that stamina and mana would be blended. I would take everything you said, add "body space", and then I think you'd have a much more realistic damage/life/energy system. Keep the called shot penalty. Maybe make a table like Rolemaster to judge where your character is hit if no part of the body is specifically targeted. After all, your head shouldn't be the only thing you can loose...