It sounds like you want a phone version of Raspberry Pi, something that's totally open to tinkering? That would be cool to see, but it would be a tough sell to general users.
I'd like a device where I can, to use a random example, trivially wire up so all messages are collected to shared database I can search, and voice messages are directed to a local or remote transcription endpoint. Or even simpler, I want a phone where I can screenshot the list of transactions in my bank app. Right now this is near-impossible, because by the time I defeat enough of "security" measures to access the data, the phone stops passing attestation checks and some of the apps in question won't load anymore.