You seem to be hard of reading and thinking.
>Yes it would because now all the drivers go to Google, not the manufacturers,
Device drivers will never ever go through Google. Even if they did it would not help because they wouldn't be getting the source code.
There are phones that phone vendors couldn't ship newer versions of Android for because silicon vendors weren't prepared to update their drivers.
>meaning Google can now push updates that don't have to go through the manufacturers
>(who actually have incentive NOT to do so: Planned Obsolescence).
So Google has some old driver binaries that no longer work with the current Android APIs and that equals them being able to test and deploy updates for phones they didn't make, have no documentation for etc? Can I get some of what you've been smoking?
>If Google don't do it, they could end up on the hook for the next big exploit.
How would Google be responsible for exploits in other vendor's drivers?
What you seem to be talking about is taking more stuff out of the system partition and making it so that it can be updated via play instead of via OS upgrades. That has nothing to do with whether AOSP is closed or not.