Personally, I think this idea is awesome. My off the top of my head suggestion would be to open source the requirements for accrediting a specific course.

For example, it's determined that students from the "Intro to Calculus for Programmers" course need to meet certain qualifications to pass. If they finish the course on their own, with no help from an instructor, then they only need pay an Instructor to oversee an "I know my stuff" exit process. If a student needs instruction, then the student can pay for the bits that they need. Instructors can become highly leveraged, experts in the parts where people really need help, charge more for their expertise, and students pay less because they need less overall instructor time.

That may be a little unclear. I've got a couple beers in me.