Sona's Tempo Powerchord rework idea

Since there has been a little talk of Sona, Probably now is a good time to post this idea again What if we gave some meaning to ranking up Sona's pointless E after rank 1?

Well what if we removed the ap scaling on her Tempo slow and reduced it's base value to 20% But here is the kicker, what if after every rank of the skill, it gains a further 20% increase to the slow So at rank 5, that would be 100%, another words it would become a root

Gives Sona's a choice in what they want to do when a game starts, do they want to be a lane bully or a semi decent peeler, this was what was so great about Sona in the past, you had so many options you could go full support, you could go AP, or you could go tanky and all would work as well as you knew your limits

Think giving Sona a root lategame (or early for the tradeoff of her doing very little damage) would be too overbearing? (not to mention Sona's winrate currently drops like a rock after 30 minutes of gameplay)

Perhaps if it is felt that way, maybe give her a scaling mana cost on her E, or remove the pathetic 1% ms per rank up on the skill, or even something like making the E projectile fly much slower so enemies can react to it