Small Phase Rush change idea

Hitting an enemy champion with 3 separate attacks or abilities grants you 75% slow resistance and (15-30)-(35.7-75)% movement speed for 3 seconds, but rapidly decaying to 30% over 2 seconds.

BUT,

The movement speed gained is based both upon level and upon how much %max enemy health damage you've dealt with those three attacks, from 35% to 70%. So if an enemy has 1000 health, and you deal 700 damage (or more) with three attacks, you get the full 70% movement speed at level 18! And if you only do 350 damage (or less), you only get the 30% movement speed.

AND THEN,

After the 2 seconds has passed, every attack or ability against a champion will increase the duration of the 30% movement speed and slow resistance by 1 second, but not exceeding 1.5 seconds (Aoe effects against champions increase it by 0.5 instead). So if you keep attacking people, you keep being fast!

In a world where Conqueror can be active forever, would this idea be too far of a stretch? I never use Phase Rush as it is, because it's just so... niche. Trading your total damage potential just so you can run away more quickly? That's just silly. I'm sure with massive changes like this, the cooldown would have to be increased to like, a minute, but it'd be exceptionally worth it in teamfights!