But only with a modified MySQL server.
But sounds great for a honeypot. Put up an easy-to-hack WordPress server, and when attacker connects to mysql, start downloading all the PII files you can think of from the client.
No, just because I don't expect my client to kill me, does not mean that therefore there is no reason to be concerned about a rogue employee of theirs being able to gain access to any other of my clients' servers that I have access to by patching an exploit into their MySQL server.
Nor is it reasonable to assume that everyone is on top of their IT security and their infrastructure is only under their own control, and that includes your own organization once it grows beyond one or two people.
If that is the kind of mental model you are working with, your IT security probably is shit. Even the slightest external vulnerability anywhere in your systems or the systems of people whose systems you access/(co-)manage is going to grant an attacker total control over your organization if that is how you manage security.