This is obviously an area where erring on the side of caution is the best course of action. For me, if the ball hits me, changes direction, and goes to another player, I'm just going to stop the game and award a dropped ball. I realize that this "overly safe refereeing" and not completely within the letter of the law, but when the ball hits me and changes direction I'm going to have a bunch of people anticipate stopping the game and awarding a dropped ball.
Here's another situation that, fortunately, hasn't happened to me yet: Attackers play a ball, and the ball touches me but doesn't have any impact on the play. The ball doesn't change direction, speed, or spin. It then goes to another attacker for a promising attack.
By the letter of the law, we could stop the game here even though the ball touching me had zero impact on the game. In fact, it's likely here that no one except me even knows that it has hit me.
If I were the Emperor of Soccer and could change this ruling (in theory), I'd change the Law wording to say that we award a dropped ball anytime the ball hits the official and "materially" impacts the game. I realize that this adds subjectivity into the decision of when to stop the match, but I like this because 1) it gives the referee more leeway to stop the match if he/she feels the touch impacted the game and 2) removes the idea of a promising attack, change of possession, ball going out of bounds, etc. For me, it simplifies the matter of stopping the match. It also removes the ambiguity of situations like in the Man City-Arsenal match or the situation I've outlined. If a Law like this were in place, I'd just stop the match any time the ball hit me and didn't go where it was intended.