For the sites that are being scanned for vulnerabilities, malware, and the like, a simple dashboard showing each application and then the number of updates and actions needed by category would be great.

This is common in a lot of wordpress security plugins.

Each row is an application/site

Columns could be
warnings/no warnings
Security enabled
Backup enabled
site is up
staging site(s)
is everything up to date
Go to admin area of the site
scan Now

vulnerabilities found

updates needed

etc.