We actually thought of doing that and allowing a manager to set custom enrollment codes but then you run the risk of duplicates and the plugin could get unwieldy.
For maintenance and other issues we really wanted to keep it as simple as possible while still making things super easy for staff and students to get into courses.
I am pretty sure that unless you are a manager you cannot delete the instance of the Easy Enrollment method once it is in your course. You can turn it off but not delete it.