Let me say I have 4 courses into my moodle installation.
I give access to each one of them asking for a fee of two Euros per course.
So if you want to enroll my course01 you have to give my organization 2 Euros.
At the same time I deliver my courses by grouping them.
To do this I added to my moodle installation two metacourses. Let me call them metacourse01 and metacourse02. Each one of these two metacourses is the collection three standard courses.
If you want you can buy the access to my metacourse01 for 5 Euros saving one Euro.
My metacourse01 collect the course01, course02 and course03.
My metacourse02 collect the course01, course02 and course04.
Well, as far as what I described, inside my Moodle installation I must have three instances of the course01.
The first instance is to deliver it as a single course.
The second instance is for the metacourse01 and its third instance is for the metacurse02.
I may have 5 students enrolled into the first instance of course01, 10 students in the second instance and 20 in the last one. The three groups of students don't share their course with the other groups of students. So this three instances of the course01 HAVE TO BE DISTINCT.
They must be distinct also because if tomorrow it will be implemented the feature request MDL-10039 they will have different parent course.
In this environment if I have to change the course01 I need to do it three times. This is really not sustainable.
My new course format suggestion is the "mirror" course format.
When I create a course and I assign it the "mirror" format I will be asked to choose the original course. The just created course will become the copy of the original course and to change it, from now on, I will only need to change the original course.
I believe it would be really useful.
Thank you for your attention.