@Stashu, You Want To Fix Cassiopeia?
Here's what you do, just scrap that passive, just ABOLISH IT. Nobody wants nor has ever wanted a stacking mechanic on Cassiopeia especially considering the fact the only other similar stacking mage (Veigar) stacks faster and can actually snowball because he stacks AP not fucking tiers to gain AP so his ratio's remain godly.
Also, stop insisting that you know better then your Cassiopeia fanbase. Dude, you have had a total of about TWO GODDAMN RANKED GAMES THIS YEAR WITH CASSIOPEIA so unless you have a smurf that you only play Cassiopeia on or their is some private Riot server then I can't fathom how you keep using this "I know better" mentality considering each time you use this Cassiopeia's rework arguably gets more laughable.
Last but not least, get it out of your thick skull that you think Cassiopeia can be a lategame hypercarry mage. For one, she's not tanky and or slippery (Like Ryze), two she can't switch targets easily (Like Ryze because he's an actual lategame hypercarry), three she's completely vulnerable and easy to crowd control (Ryze is naturally tank and a kiter and Fiora can go untargetable while facerolling your entire team), and lastly four she's not fucking mobile.
It doesn't matter how much you tweak her kit or that pathetic excuse you call a passive she is never going to be this lategame hypercarry that just seems to be a ADC that happens to build AP, cannot destroy towers, and needs to poison targets before she can use autos that cost mana.
A
IMMOBILE
SQUISHY
MAGE
THAT
HAS
MANA PROBLEMS
AND PROBLEMS SWITCHING TARGETS
WILL
NEVER
EVER
BE
A
LATEGAME
HYPERCARRY