As the Martial Options homebrew has gotten a bit too big for its own good, I've decided to split off the parts I like and work on them separately. That way, instead of a mishmash of options, people have access to smaller, more specific subsystems to use in their games.
Anatomic Combat is one such system. It's my take on "called shots" for 5e, integrating it as part of each attack. While not spelled (heh) out directly, this is intended to affect both weapon attacks and spell attacks, such as from shocking grasp and fire bolt.
You can find it embedded below.