A tricky area.
I've been involved with several MCC, JOC and Combined courses, both for modular students and also airline cadet specific company versions.
TBH, its all a bit of a muddle. I seriously doubt there has every been a proper training needs analysis done on most of these things.
I've also been involved in initial setup, and had to deal with intransigent regulators insisting on jam packing them full with everything under the sun until it becomes almost a mini type rating.
A few observations in no particular order.
An MCC on a complex jet inevitably will end up including some JOC elements.
A JOC on a multi crew aircraft will inevitably include some MCC elements.
Basic handling skills are required otherwise the students don't have the capacity to learn the multi crew stuff. Not least, being an effective multi crew with the automatics out requires different prioritisation and workload management.
Students inevitably want to use the course as interview sim check prep.
In my experience, everyone want to cram as much stuff into the course as possible.
The best analogy is this:
https://www.youtube.com/watch?v=aXQ2lO3ieBA
But instead of armoured vehicles, think flying training.