Also, I don't think that players will be able to see their feet (even when sliding) since in every video that shows players sliding, feet are not visible. It may add to the "realism," but it add nothing to the gameplay and can essentially detract from gameplay, having feet visible on screen while players are trying to shoot, slide around, so it is essentially....useless.
The problem with that is, the videos where they actually slide, don't even have a visible HUD. I looked before I asked the question. So who knows, It might be in the game, it might not.
Also in most FPS games, you can't see your own shadow. But in Brink you can, so I think it would be a little weird to look down and see your shadow coming off (being created by) nothing.