Kassadin: Anti-mage Assassin?

i think kassadin needs to be given more tools to fight mages and I'm not talking a total massive powerboost but some love in the department to fight them would be nice. I was talking to my friends about giving him more damage against "Mage type" champions and i came to an idea that Riot once employed on Veigars ultimate. The idea of Kassadin being able to utilized the enemies Ap against them fits with his core dynamic of being anti-mage and im not talking giving him a 100% or 80% or even a 50% Ap scaling I'm talking maybe a max of 5%- 20% on his abilities based on his rank of ultimate. I would really like to hear back from anyone at Riot about this idea. Please and Thank you. Korisue