Ekko, the assassin. Or is he?
I mean his base values on the PBE are so low and the scalings are so high on everything but his ult.
He theoretically can be the first melee ADC in league. His procs for magic damage give him mixed damage. He has a shield that slows and stuns giving him edges in trades. His ult would allow him to take advantage of cocky ranged ADCs who thought they had the lead when he was really just setting them up. He has a gapcloser to get him into fights
I feel like Ekko can easily be played as an ADC although it would require playing a much different style.
and so on. They're played more like assassins, but they're carries of attack damage all the same. Just like you're talking about Ekko possibly being one, they already do that. Zed too, since he does split-push reasonably.
, has a powerful %-based on-hit, as well as an AA reset that double procs on-hits and lowers its cooldown on AAs - these two together function as her "steroid". Ekko has... three on-hits, only one of which does good lategame damage without AP, his W passive, but even that one is much more effective with AP (that ratio is fucking ridiculous right now, and they've already nerfed it a bit).