Many people want control over whether they back up conversations with others, and think it would be crazy for sender to control the retention policy instead of receiver.
I think sender should just be able to send a recommended preference hint on retention and you could have an option to respect it or not.
Yes, but they'd have to issue another one of these snooping demands to either the app's developer (there's loads of developers so this would get out of hand quickly) or to Apple to patch the build or read the memory or something to get the unencrypted data
This current demand isn't blanket access to your device, it's access to things uploaded to Apple's online storage service. Having to get a backdoor that works with every app's encryption takes a lot more work while running the data through an authenticated encryption algorithm is relatively trivial for a developer
Really, apps should encrypt their own storage with keys that aren't stored in the backups. That's how you get security/privacy back.