I have just created an script to reset courses on bulk. I only need to specify a condition for the courses, can be all, and the roles that I want to clean. So far so good, but I have only try it in a development version of Moodle. I would like to have it ready for next semester. I'd be interested in more people, may be developers, cheeking it. If you are interested please contact me and I'll gladly pass you the code.