Brainstorming: A Healthier Version of Kog's W
As I'm sure you've seen already, Riot is reverting Kog's W back to pre-rework because it's basically impossible to balance as it was. That said, I still like the concept behind it, so I was thinking about whether there was a way to actually make a workable version of it.
Considering the qualities of Kog's W:
- Instantly doubles both Total Attack Speed and the AS cap upon activation.
- Grants bonus Attack Range and %HP magic damage.
If one were to make a better-functioning version, it would require proper build-up, as well as not having so many extra features, namely the bonus range and %HP components. Therefore, it would make sense as an innate, I think. Then you can balance the champion around the idea of them buying many on-hit items, rather than try to balance all the on-hit items around the idea of the champion buying them.
Passive: Particle Acceleration
Any bonus Attack Speed that Seles gains from other sources besides her own Level or the effects of Particle Acceleration is halved, with the other half instead increasing her Attack Speed cap, up to a maximum cap of 5. (Ex: If Seles gains 40% bonus Attack Speed from other sources, half of that instead increases her Attack Speed cap, putting her cap at 3.)
Whenever Seles attacks an enemy unit, she gains a stack of Particle Acceleration, up to a maximum of 10. Each stack increases her Total Attack Speed by 15% and reduces her Basic Attack Ratio by 5%, applied additively.
If Seles becomes afflicted by hard crowd control or leaves combat, the stacks reset.
Seles is a placeholder name I use for all ADC concepts I make, in the hopes that I can one day actually conceptualize an entire kit for her.
At maximum stacks, she'll have gained 2.5x her original Attack Speed, while her basic attacks only deal 50% AD base damage. This makes it slightly weaker than Kog's activated W in terms of raw damage, before factoring in the exclusion of any %HP damage as well.
For the first part, Seles would need to gain 200% bonus Attack Speed to cap her maximum AS at 5. Let me look to a usual on-hit Kog build to check numbers...

42 + 40 + 40 + 40 + 35 = 197%
With runes/masteries, Seles can cap Attack Speed at 5 at around full build, so her mid-game shouldn't be ridiculously dumb like Kog's can be.
(The losing stacks when crowd-controlled thing is a bit of a flavor thing, but I think it works nice for balance. She needs to be able to vent power to prevent overloading, and she can't easily vent when her movement is restricted, so the entire thing is discharged at once.)
Anyhow, this was just brainstorming. I really like the concept of a high-speed machine gun type, a champion who actually can build all on-hit items and work. _(I'm sure Kog CAN still run all on-hit to reasonable effectiveness once reverted, but he'll likely go back to running Trinity Force like he did before the rework.)_