What is the false positive rate that you would be comfortable with such a scan having? What would be the risk of your personal photos and videos being recognized as CSAM and reported to your local police (and thus being shown to your local police) that you would be happy to accept?

Would you also be ok with not being allowed to send any mail unless you first scan the contents of everything in that envelope and include a generated signature that might tell the post office that you're sending CSAM? And then having the envelope delivered directly to police if the scan did indicate that?