Now hear me out on this ok. Being able to permanently cc someone is fun. However being able to "chain" that cc with no way to escape isn't. Lets take an example of Lux and Morgana in a lane. Even better example is point and click cc champs. You get snared by either, you might as well kiss your ass good bye.
So what I propose would be this. Much akin to the Shield Overload. A special debuff named "CC Perseverance" where if you're hit by a spell that inflicts hard cc. For the duration of the 1st spell nothing happens, but if you're hit by another spell that applies the same or different form of hard cc. A stack of perseverance is applied, this stack add's an additional 15% tenacity and can stack 3 times. Before you throw in the argument about Irelia and Mundo. They already nearly surpass 60% tenacity with mastery, boots and individual passives. This idea is simply something I thought of to help make the game slightly more healthy. Because come on no matter how good you are at this game. Theres no way you can sidestep enough to dodge fast traveling skill shots like that. Eventually you will be hit, you will be permanently cc'd and you will die. That isn't fun, it is downright annoying and makes you want to stop playing the game.