Hand to Hand specialization
Focus on which part to use

I propose an idea that I'm not quite sure how it can be or even if it is possible to implement

But how cool would it be to specify whether or not you want to use the upper or lower region to exclusively fight with.

It could be an interesting way to change up combat. Like a character wants to exclusively kick or exclusively punch.

If you look at Capoeira as an example…

What you are talking about is basically styles. From an RP standpoint, some martial arts favor punching while others favor kicking or grappling or whatever. There are more than two styles and its better than having one punch man style and roundhouse kick cowboy style. At the end of the day, its mostly flavor.

That being said, if its RP you are after and not vague bonuses then you can develop your own style within a style, make triggered emote macros for combat and even start a dojo.