Whether or not a System User is Active can be read from System administration object. However, when the state of Active is changed in System Users, no Signal is caught using Record Modified if the Active flag was changed manually in System Users. The Signal only triggers a process if the Active status is changed by another process.
How can a process be started when changing the Active status of a System User manually?
Unfortunately, you wouldn't be able to put "Functional role" as a value of "To" field of the "Send Email" process element using user tools. Our R&D team already working on adding this functionality, there is no ETA yet, however. You may build your process analogically to the "Send email to case group" base process that sends email to a group of people using script task.
Here is also another solution that can fit your needs: you can specify one recipient in "To" field in the business process "Send email" element and on mail-server side you can setup filters which will transfer notification emails to some specific folder and then mail-server can transfer all emails sent to this folder to other mailboxes. And it will fit your business target. But I will notify our R&D team about your request and ask them to raise the priority of the problem.
