Rengar's new W got me thinking

Why not do the same to 's passive. Hear me out, I know that Sion is good in top lane and really good as Support, but his passive is really bad/useless 80% of the time. I know that Sion's passive can be used to steal some of the enemies' camps, and it can do just enough damage in laning phase to kill the enemy. However, most of the time, and especially in teamfights, people just walk away from you, since it takes quite some time to "respawn" and then continue to cc you to death (again). Adding this CC-Break effect to his MVSpeed ability in his passive will really help him to break free and actually doe something when being in his passive. He doesn't really need the cc immunity Rengar gets, but it can still be anoption. With this effect his Passive won't be as laughable as it currently is, I mean it's called "GLORY in death". Some of you may ask, that if he already has such a good win rate adding this effect will just lead to nerfs on other abilities in kit and create the risk of unbalancing a well designed champion, but I think buffing an ability that represent a champion and his lore and making it actually useful is important, too. He's called "The undead juggernaut", his Passive is the only ability that represents that, but it's the most useless imo.