I think if it was Amazon it would probably be exclusive Amazon Appstore instead of exclusive Amazon Tablet. Maybe exclusive Amazon App Store plus free on Amazon devices.
(1) Amazon's central business is the store, and something like this could be a loss leader to help build the Amazon Appstore vs Google Market.
(2) 90% of the value in these companies would be lost if you lost all phone sales (hence Rovio's short term exclusive on AB2).
Amazon bought Reflexive Entertainment, so there is a precedent of Amazon buying games companies. Afaik they moved a lot of the developers to A2Z Development, but I think they'd leave Popcap largely untouched.