Stuns should not stack
For example, if I get stunned by Riven's Ki Burst, I should have a one-second immunity to all forms of cc and not get stunned again if Sejuaini uses her ultimate on me by putting me in a perpetual cc instakill. Counterplay should not be Cleanse or QSS because these are all too unreliable. Mercury treads is also not a perfect solution because it only reduces cc by 35% which is not enough.