The app covers on the home screen do this, and - in my opinion - in a better way than animated icons would.
What advantage would we get from looking in the app drawer (with lots and lots of icons, potentially in folders) instead of the home screen (with just the currently running apps)?
Thank you for the background to your wish! Unfortunately, I’m not familiar with the N9, so I still don’t understand how it is different from the current app drawer, why it would be better along the vertical edge, or how you think it would fit in with existing navigation.
Or did you want to replace current navigation with how it worked on the N9? Then I think you need to cover (edit:) all the other parts as well, not just the app drawer.
(Edit: Missing words in last sentence made it hard to understand.)