Just a thought about balancing mobility creep... And the gapcloser problem.

What if applying slows could reduce the MISSILE SPEED of blinks/dashes by that much during the debuff?

For example, Thresh's Box, if hit by a champion with a gapcloser, would reduce the speed of all dashes by 99%(capped so actually less) that the victim uses. The victim will be moving away in slo-mo while the enemy will finally be able to catch up.

Obviously Thresh and Zilean would make this ridiculous, so the numbers may need some tweaking, but this would sort of alleviate the mobility creep for everyone not named Veigar(even him, actually), would it not?