Imo the part about sending players off if they are deemed to have no opportunity of playing the ball would likely lead to more confusion, slo-mo replays of incidents, calls for video technology etc., as how many times does a player make a challenge with no chance of getting to the ball? If you're close enough to pull a shirt or bring someone down then there's no reason you're not logically close enough to get to the ball.
However, agree with the 4th substitute in ET ruling. Always thought myself that teams should be allowed to make a 4th substitute in normal time but only in case of injury. The way it is now, if a player injures a member of the opposition, then his team are rewarded in a way by being a man up.