Maldet for linux inside Plesk
is better if such as "wordpress toolkit" you implement this software in plesk https://www.rfxn.com/projects/linux-malware-detect/ + ClamAV (is more faster the maildect search).
With this way, anyone can scan our website from malware. And after scan, the user need to have an notify via email or directly into plesk. This inscrease the security of website and also increase the plesk security.
I use it somethimes for scan all website into our web hosting, and I found it very usefull for prevent serius problem of botnet, hacked website etc.
I hope that you can consider to implement this function.
Maldet is good solution with Malware.Expert - PHP malware signatures - https://malware.expert/signatures/
I use it as a cli and would be nice to see it on Plesk.
Totally agree with the need for a Malware detect tool (LMD + ClamAV will be perfect!).
Also a plugin that allows a user to suspend a domain name if malware detect find nasty stuff under its account.