I was hoping to do this but ran out of time.
Basically this is about moving the config for enrolment instances to the enrolment management overview page.
1) Remove all the enrolment instance config from the "Course settings" page, EXCEPT the one for guests. All the plumbing for this (the stuff that looks for the course_edit_form() method in enrol/xxx/lib.php) can stay, just remove all those methods except guest.
2) Add an "edit" icon to the final column of 'Enrolment methods' : enrol/instances.php?id=x which links to enrol/config.php?id=X
3) enrol/config.php?id=x could do something similar to what the course page was doing, ie looking for a method like course_edit_form() to produce a form, and then using a companion method to validate it. Usually it does only one instance at a time ... perhaps if you call it as enrol/config.php?courseid=y then it would show all of them at once.
4) Whenever we create a new enrolment method instance, we should automatically redirect to the config page for the new instance.