% damages, add in ability power ratios so they have some kind of scaling value for player choice.
W heal, add in an ability power ratio.
R heal, add in an ability power ratio.
The reason why AP ratios exist is so that something does not have all base value and no ratio.
Passive damage, add in a juicy and meaty AP ratio.
W damage, add in an AP ratio, possibly the slow as well.
E passive healing, adding in an AP ratio.
Again, these are abilities that make sense to have AP ratios.
Add AP ratios to ALL of his abilities. These abilities should be AP only and Pyke should have an on-hit damage that scales with only AP, but at the very least make them hybrid scaling. This would fulfill the squishy aspect that you want out of Pyke, help keep him balanced, and do it without weird mechanics.
You have a system where abilities scale with a specific stat, and you forget it even exists and the purpose of it, you NEED to be utilizing ability power a lot more and implement it to all the abilities and take away AD ratios since AD was meant to be balanced around the fact that EVERYONE has a 100% ratio on their basic attacks and ability power is balance through each champion's ratios and allows you to tune the base damage and ratio and decide where a champion's power lies and when they are weak and strong.
There was a reason why champions used to only scale with ability power. The design decision back then was good and you knew what you were doing, now if you have not a clue of what to do anymore. Champion balance was out of wack, but the overlying system in place was solid and just needed tuning, tweaks, and game health improvement changes.