Lissandra Passive Idea

I heard Riot is looking for a more impact full passive for . SO i thought I would throw my idea in and see the Response.

Passive - Cold's Embrace Lissandra's Movement impairing spells will Auto Execute any champion that is below 5% health.( This threshold is affected by Magic Resist/Penetration). The threshold is increased by 5% for each unique champion killed by this effect.

Notes:

• Since this threshold is affected by MR that means if you have 100 mr and Lissandra has no pen then the threshold would be reduce by 50% just like how it works with magic damage.
• *The same is true if you have 0 mr and Lissandra has 100 pen the threshold would be increased by 50%.
• *The thresh old is only increased if the passive kills the target. So if you over kill them it does nothing.
• *This passive will only trigger after the damage from the spell is done.
• *The passive will ignore physical and normal shields when calculating health percentage but Magic shields will count as health in this instance.
• *Also i think her q should be changed so only targets hit before the shard shatters will be slowed. *This will reduce the range where she can auto execute champs

Let me know what you guys think.