This "attack" is not even theoretical. Android apps can just download arbitrary binary code, mprotect(PROT_MAYEXEC) some area in RAM, link the code there, and run it.
Google will simply revoke the keys for the "loader" APK. But that's fine for malware, its authors will just use the next stolen credit card to register a new account.
That's also why this has nothing to do with security.
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