The PBE Elise Neurotoxin change would be cool on Cassiopeia.

I think the general consensus on Cassiopeia is that she should be a poison mage rather than a machine gun. It would be cool to have something like Elise's PBE neurotoxin "Poisons an enemy for 3 seconds dealing 20/30/40/50/60(+.15 AP) magic damage each second" instead of spamming twin fang.

The numbers of her kit would have to be adjusted accordingly since most of her power is her twin fang obviously, but this is a great way to give Cassiopeia that "Don't come near me I'm a spitting cobra" type of gameplay. Harassing and zoning, and also stacking her passive. She blasts an aoe DoT and then a targeted DoT that you can refresh every few seconds for perfect zoning.

In my opinion Cassiopeia's Miasma and Noxious Blast are perfect for her kit. Even her ultimate is pretty well balanced and fits thematically. If we could change these abilities along with a neurotoxin-like ability to all be equally important in her gameplay, she'd be an awesome poison mage.