How to change Ekko to make him the AP assassin he was supposed to be

Kinda getting tired of seeing Tanko in so many pro-games. Repeated nerfs have not hindered players from playing him. Riot has stuck with the "Nerf the base, increase the scaling" mantra, which simply hasn't worked.

What makes Tanko strong isn't the damage, it's the kit. Here's whats great about Tanko-

1. HIs mobility
2. His CCs, multi-stun, plus slows from Q
3. His stickiness (due to movespeed through passive, the continuous slows from low CD Q and the phase dive gap closer)
4. His tankiness and the ability to disengage with his ult if he does mess up. Usually tanks, if they make a bad engage, they pay for it, but not tanko, he can just ult out.
5. His waveclear. For a melee top laner, Tanko has incredible waveclear because of his Q. Not many ways you can punish Tanko in lane.

That's not what a brusier or a tank is supposed to be. Those are the hallmarks of an assassin.

Now, how do we turn Ekko in to what Riot intended him to be? Hit him on the CDs! How without hurting AP ekko you ask? Well...here's how.

1. Give him an additional passive, for every 100AP maybe (every 80AP), Ekko gains 10% CDR. But! Ekko can't gain CD through items. Gets 40% CDR around 360-400AP, which seems reasonable
2. Then again, Zhonya's, Abysal is kinda crucial for AP Ekko, so the 20% CD would be wasted? How about that new passive would also convert CD gained by items in to AP. For every 10% CD gained through item, Ekko gains 12AP. (it's gold efficient trade btw)

What will this do? This will make Ekko viable only as an AP assassin. Bye bye Tanko. No way can Tanko be impactful without CDR on his abilities. Ekko will be played as he was intended to. Flashy high risk high reward AP assassin. The kit was designed for that purpose but is being completely abused and misused.

A problem with AP scaling CDs though. His early levels could be hurt? Hmm...how do we address this?

Maybe Ekko gets 10%CD on 50-60AP 20%CD on 140-180AP 30%CD on 240AP-280AP 40%CD on 360-400AP