That would be a great feature. I currently, as admin, upload all users but have given teachers the ability to add/delete existing users from their courses as I also do not want them being able to affect other users. The problem is that user import is a system wide process designed for bulk import and so there are no limitations by course or group. A course specific import or at least an easier gui for user adding would be a great feature. I suggest putting a request on the tracker and then post the link here so that we can vote on it.