For those who may want it: I’ve written a script to remove the existing Malware Remover QPKG, and prevent it being re-installed until the NAS is restarted.
Use it along with the RunLast QPKG for boot-persistent automation.
Update: tested OK as far-back as QTS 4.2.6, and on Malware Remover versions released from 6th January 2023 onward.