An important feature addition would be the ability to annotate pdf/documents within the student app similar to how teachers can mark up student work in the app. Teachers could then post handouts/documents for the students, they could open them in the app as they can currently, and then they could annotate and save their marked copy to either their own resources or submit back to an assignment. It would seem this would be doable as the annotation ability is there for teachers.
Currently we are using a third party app for annotations and could then cut out a step in the workflow. We use notability. Another option would be to have a notability app widget similar to the drive widget that would allow students to move things back and forth.