An easy solution to all item balance issues plaguing the game. Serious feedback.

Restrict items. Don't want mages building rylai's? restrict the item from the champion class buying it. Don't want an entire class to lose access to an item? narrow it down and restrict it to trouble makers only. Want to add in an item/tune a current item for a specific champion? Restrict the item to only be purchasable to that specific champion.

It doesn't even need to go all the way to restricting the items themselves. You could restrict the passives to specific ability/champion types. They did it to the Hydra set and Runaan's and also have varying passive affects based on if your champion is ranged or not, so why not take that effect a step further?

Take PD's damage reduction passive to ranged only and boom, there goes the yasuo complaints. Remove access to rylai's passive from Cass and there goes that issue. Rather than having to balance the game around specific champions making a particular item too strong, this option allows so much more freedom with item balance without worrying about it breaking the game.