fears - 4 champions in game
taunts- 3 champions in game
blind- 2 champions in game
polymorph- 1 champion in game
silence -6 champs atm but im preety sure that soon it will be like 4
and 3 of those effects are used for the similar effect to stunn
too little pool to bother
knockups just get more popular (if champion has to have some reliant cc they give him cc that cant be reduced, on the other hand any additions to his kit that does not need to be reliant are made into reducable cc )
Aatrox, alistar, azir, blitzcrank, braum, cho, fizz, janna, jarvan 4, Lee sin, Lulu, Malphite, Nami, Nautilus, Riven, Sej, Vi, WUkong, Xin Zhao, Yasuo, Zyra
Blitz has to use a high risk, high mana move to do a knock up
Riven, Aatrox, Braum, Cho, Yasuo, Janna, Sej all have telegraphed, dodgeable knock ups
Braum, Fizz, Lulu, Malphite, Nautilus, Nami, lee sin, vi, Wukong, Zyra have to use an ult for a knockup (some are also telegraphed)
Xin has to hit 3 basic attacks to get a knock up, J4 has to combo 2 abilities (also telegraphed and dodgeable), Riven has to Q 3 times.
Out of all of those I would only consider Malphites, Wukongs and Zyras knock ups prone to toxicity.
Velkoz E doesnt count as a knock up and actually interacts with merc treads in reducing his abysmal 'knock' up duration already (0.75 seconds) since its considered a type of stun
Nami Q is considered a stun and gets reduced by merc treads.
The amount of stuns, roots, slows greatly outnumber the amount of knockups in the game and are generally applied much easier, faster and with less telegraphing or combo mechanics. In a game where a champion is causing considerable annoyance with a knock up I would advocate a spell shield (banshees veil).
Knock up champions ninja tabis / banshees veil would work for: Aatrox, J4, Riven, Xin Zhao, Yasuo
So 5 champions.
Edit: out of these champions only Aatrox and riven realistically go top. J4 and Xin Zhao are relegated to jungle pretty much and Yasuo is a mid champ.