Hi Mathieu,
Unfortunately I can't reply in-depth - but in regard to workflow changes (e.g. your scenario 3, "Revise the submission workflow so that fewer steps are involved"), I think we'll never be able to find one workflow that works for everyone all the time.
As such, I think we need to further develop the workflow system so that we can customize the workflow, writing new workflow configurations according to course/institution requirements.
You might like to read MDL-44565, which looks at this.
Cheers,
Dave.