AWS is at least as important, as is Akamai.
My point being, it's not enough to hand-wave about who's the biggest and most important. A good system would give anyone with enough at risk a clear path to earn a seat at the table.
Major providers could create an "early warning disclosure club", each contributing some money annually, and the money can be used to pay bounties to anyone who gives them advance warning of a zero day. Of course you'd want some safeguards to make sure nobody blackhat joins the club to use the vulnerabilities for offense.