If I could update Kennen I would make him more of a Marksmen type ninja with better AD ratios.

Id start by Strengthening his passive but giving the 3rd stack application an on-target cooldown starting at 8 seconds then lowering to 7/6 at levels 9/16, and add level-scaling magic damage to the proc at around 30-110(+30% Ap) while keeping the stun duration at 1.25 sec and increasing the Energy restored to 40.

*This mechanic is meant to gate the stun and damage but allow the continued use of his W active and priming for a potential second passive proc after cooled down.

I would reduce the base damage and Ap scaling of his Q and add an AD ratio from 75/115/155/195/235(+ 75% AP) to something like 40//80/120/160/200(+70% AD +50% AP), or possibly bonus AD scaling.

Id keep the W active relatively the same but would have the W Passive Proc every 3rd attack instead of 5th.

As far as his E and R go, Those ability's can most likely be untouched but if any numbers need to be reduced it could easily be from those 2 spells and even W active.

This would make him similar to in the hybrid marksmen category, while not only keeping his unique identity but improving it.

I can only hope.