Ashe Passive Has An Easy Fix

What would happen if Ashe gained a stack of Focus for her passive whenever she killed a unit?

It takes 3 seconds for the passive to start up again whenever she attacks, and even if you get the last hit you're still delaying an opportunity to crit; you're only getting some recompense once you put a point in your E, but then there're enemy champions and harassment to consider. Any aggressive lane won't give Ashe the time to save up for her passive if she wants to keep up, as she can really only charge it by either not cs'ing or being willing to stay back. One may consider staying in the back since there're more costs than benefits if you don't W, but keeping up with the minion pressure in lane leaves her passive useless again. Her first auto attack from base probably won't be trained on a champion either if she wants to keep up her gold income.

Ultimately I feel that allowing her passive to stack on unit kill helps her endure tough lanes and further promotes cs'ing.