Make Phase Rush the old spellthief's quest reward

Phase Rush is a keystone very few champions use effectively because most champions would rather have something that allows to poke the enemy or burst them down if they need to use 3 or more abilities. Unless you are a champion that spams abilities why would you want to use three abilities just to be able to run faster. How about instead make it like the old spellthief's quest reward, here is old spellthief's reward:

QUEEN'S TRIBUTE: Spells and basic attacks against champions or buildings deal 15 additional damage, grant Gold 15 and 50% bonus movement speed for 1 second (additional stacks extend duration). This can occur up to 3 times every 30 seconds.

This was one of my favorite items to use because it felt really satisfying to be able to suddenly run fast and kite the enemy as a mage. I do think the quest we have right now is better because I don't have to spend 800 gold on sightstone and instead I have to participate in the lane in order to complete the quest which makes the lane more exciting.

However I do miss the quest so instead why not just put that old quest on Phase Rush so you don't even have to play support to get the benefit of this fun effect. It gives you the ability to kite as a mage in sacrifice you don't have the poke from summon arey/ arcane comet or the burst of electrocute. Although I do think having 50% movement speed early in the game would be op so maybe instead it should be like 20% movement speed at level 1 and scales up to 50% movement speed at level 18. I'd like to hear what others think about this suggestion.