[Call me when humans go extinct]

Yeah, it's nearly impossible to make the headshot mode toggled individually using the existing plugins. Because the headshot plugins are basically to restore players' HP to 100% within 0.5 second or so after getting hit. Only damage dealt over 100 can kill players. So it's every hard to achieve individual togglable headshot mode without touching the source code of the game. Only plugins can't make the damage giving by one player to the other be 0 while hitting the body and 100 while hitting the head.