I think sparking interest would come from the direction of programs who are trying to get their students to apply for internal scholarships. That would generate a base of people doing scholarships in this way. Putting together data and testimonials from earlier groups would make it easier to go pitch the big groups.
This is a nice approach as it gets to the core of what knowledge is. If you can complete an examination that meets the essential standards for a course you should not have to pay full price as you have already done the work. This also reminds me of the Cambridge Institute of Examinations model.