Cassiopeia passive suggestions

With all the talk of the possibility of a second gameplay passive to accompany her current passive, I kept thinking of some cool passives that could possibly fit with Cassiopeia.

Deadly Cadence (revised)
Hitting an enemy champion with a  spell causes any subsequent spellcasts within 3 seconds to cost 30% less mana. Does not stack.

Now with the ability having to hit the champion, she can't have 50% mana costs at all time just by hitting noxious blast on the ground. This passive could allow her to harass her enemies with twin fang after hitting a noxious blast (both poison and passive last for 3 seconds) without making her go OOM easily in lane

Shed Skin After taking lethal damage, Cassiopeia turns into stone (much like zhonya but like, stone-looking) becoming invulnerable and untargetable for 1.5 seconds, after the duration ends her stone shell explodes, stunning people in a small aoe around her and giving her a shield and 100% bonus movement speed boost that decays over 2 seconds. Has a cooldown.

With Cassiopeia's lack of range and on-demand mobility, this passive will save her when enemies gang up on her or when she is cc-locked and bursted easily as she has to get herself in dangerous range to fight.

Viper's Kiss
Cassiopeia's basic attack throws a venom gorged asp that deals double the auto attack's damage as bonus poison damage over 3 seconds. Has a cooldown.

This passive gives Cass a more reliable way to poison her enemies for twin fang since her poisons are skill shots and she has a difficulty switching targets.

Do you like them? Do you hate them? Tell me what you think.