Ready to ruin the security of Linux, you mean. The split between package vendor and package maintainer has classically been the primary reason for malware being rare on Linux. Getting maintainers out of the loop for auditing packages, ensuring security updates go out, etc - is an awful idea. Sandboxing applications is great, but it can be done without subverting the package manager.
>Getting maintainers out of the loop for auditing packages
Do maintainers commonly audit source code to look for vulnerabilities? And at any rate, aren't the common security-critical libraries for flatpaks, like OpenSSL, already (in theory) provided and maintained by the runtimes?
All the major consumer OSs distinguish between system components, like cryptographic services and graphics libraries, and user-facing applications. The world hasn't collapsed for them so far, and in an ideal world that distinction allows for better delegation of responsibilities.