redjam
You should keep the course realistic. For my essay, I actually thought about what I wanted to learn and what didn't already exist. I have a real need for the course that I suggested so hopefully when I go to Wharton, I can actually create that course.
Hope that helps!
Second that. Be realistic. My opinion: you don't need to nail down all the details about the course, but should keep it realistic. For example, if you want to plan a field trip, it is not so long that it impacts other on-campus courses... I think it's good idea to add details (such as who to teach, what specific course delivery method is) because it shows you know the course, the Wharton and most importantly, your need of the course.