Asking for corki change

Hi, I wanted to ask what would happen if corki E instead of flat armor pen/magic pen it has a %pen. Corki set up is suppose to be weak early for scaling harder but the nature of his magic dmg make him a weak pick against mr user. Since his E is a dot effect I tough it would be better if he was rewarded with %magic and armor pen making him to still play through late game (losing a bit of early and mid game). Getting a void staff for dealing with mr user fell to unsatisfying on my hand since his ap ratio are so weak and the ap doesn't scale with his passive.