What if *certain* champions could slow dashes as well as normal movement? (not asking for buffs)

Lots of champions with a utility, kiting, or CC focus tend to counter melee or immobile champions really really hard unless they have a lot of mobility.

What if those some of those champions with a particular focus on slows, kiting or soft CC peeling had their overall slow numbers reduced so immobile champions aren't countered as hard, but to avoid making them just weak in general, they can slow dashes too?

An example would be Zilean - if Garen, Darius or Mundo try to close in on the ADC, it's an instant lose for them unless they stack lots of slow resistance or tenacity. Zilean uses EWE on the juggernaut and the ADC and the speed advantage just becomes too large. So what if the slow was reduced to give juggernauts a better chance, but at the same time to avoid making Zilean useless, it affected mobility if he used E both times (in his EWE combo) on an enemy. Another example would be Ashe, her balance is almost completely, if not entirely decided by the strength of tanks and juggernauts, and how weak assassins and divers are along with the amount of tenacity or slow resistance in the game. By making her unable to completely counter tanks or juggernauts, but able to fend off divers and assassins given enough help, her balance becomes much easier as she becomes a more generalist utility pick rather than a champion that's either a hard counter, or hard countered.

It would also go a long way to balancing slow resistance in general, they can be lessened in swifties and tank items but can afford to appear in more places as being high slow resistance is no longer a necessity against champions like Ashe as a tank.

And it might make things harder for assassins but in exchange they get better itemization that ADCs can't abuse as much with the exception of Vayne, Kalista, Kindred and Lucian (not worth on long cooldown dashes for ADCs). Slow resistance on dashes + high lethality + low AD, it can bring a new line of anti-support items for assassins while not breaking either side.Or maybe it can be an AP assassin item. At worst their mobility is no longer paying an extremely high cost in their power budget and they can actually afford to be given better burst as any delay added in the assassin reworks can be removed as the delay will be in the dashes themselves

This won't apply to all champions of course, and definitely not on any slowing item.