The original Rainbow Six games called, they and SWAT4 are very hurt that you forget that they did that years ago. And very few people liked it since it knee caps fast paced action multiplayer.More reaction to bodily damage, in both multiplayer and singleplayer shooters. You get shot in the legs, your character is limping now. But it's not just, hey, you're slower now. You hobble, your vision bobbing as you move, your aim is worse when you move, your gun swaying heavily. Getting shot in the arm with a high enough caliber would make you lose function of that arm, forcing you to use your side arm permanently, and making reloading take much longer.
And of course on the flip side, seeing your enemy react similarily, especially in single player experiences. We need more people crawling away after losing their legs and other such dismemberment reactions in video games.
However, it would be a very neat option for a sort of hardcore mode multiplayer shooter. Which ironically is exactly what Rainbow Six used to be.