Allow students Auditing or Assisting a class on a list below the class list

When you are in a class and click "students," I would like to have a section below for students Auditing, Assisting, or even just "Other" students. I have many students who Audit a class level above or lower than them. They are not in the class, nor in recital, but regularly come to the class and I would like to be able to keep track of them. If the option was "Other," I could even include student assistants on this list without them being listed as a "Student" in the class.

This would be so helpful. Thank you.