We are using a Managed Service Account to run SQL Monitor so we don't have to manage passwords. However we still need to have a regular domain account to query AD because there is no option other than to specify a username and password.

What would be great is to have an option to use the base monitor service account to query AD instead of having to specify a username and password.

This would work in a similar way to what already exists when setting up credentials for the server you monitor, where you can choose to connect to the host machine using the Base Monitor Service Account. It doesn't replace the current username/password fields that are there for environments that need to use a different user.