Being able to reset a password and email to student user the new password via a workflow depending on conditions

We have returning students who need to complete online assessments. However, when they are booked into a workshop they are not sent the system generated new user email containing username and password as they are already set up as a user from their previous training. 

As we run short courses students are required to complete online assessments each time they come back to complete training. We use the new user email to instruct the student on how to access the student portal and provide them with their username and password. 

There is no way they are going to remember what their username is and password so the best option would be to be able to send the new user email containing the username and new password each time they are registered into online assessments. I understand that this would not be suitable for all RTOs so having it as an option via a workflow would work best. Something like..

Send new user email (with reset password)

When booked into a specific course type (or online assessment enrollment) 

Some more thinking may be needed to consider the best options, however, only being able to send a new password to a user by clicking the reset email button on the user management page just seems very restrictive. 

Another option would be to have a workflow that can delete the student as a user once the course date has passed or when a student has completed an online assessment. I know this is possible in other LMS's. That way when they are enrolled in a course that requires online assessments in the future, the new user email will be sent again.  

Our only other option at the moment is to manually delete the student as a learner when we are processing each course. This is a very time consuming process!