I’d love a course that focuses specifically on design, maybe with some emphasis on creating and continually updating a game design doc as you go along. I am thinking this could be an advanced course which assumes a lot of prior knowledge - students should have at least taken an intermediate course.
The focus can be more on how to plan, take small bites, and not get overwhelmed by an ambitious project. Along the way of the course the instructor will take on a big project and show how they use their design doc to guide their work. At the end of it, the course should only have you complete a small fraction of what’s in the design doc leaving it up to the student to complete the rest in whatever way they desire.