I personally have pondered this many times. It would be taking "fighting style" to the next level. Instead of it simply being determined by how you play and what weapons you use, you could actually choose how your character fights. How will you hold your knife, blade up or blade down? Are you a lefty or a righty? Even something like whether you dolphin dive, knee slide, or straight up baseball slide could add an immense amount of immersion for players. It really is in the little details.