I agree and have had a similar idea for awhile. Have the best lecturers for given subjects create outstanding virtual courses, develop sets of curricula off of those courses, and have TAs (PhDs in your model) provide local instruction and tutoring to augment the standard coursework.

It seems crazy to me that we have thousands of new faculty members and PhDs begrudgingly spending time developing their own way of teaching material (instead of working on research which is what they actually want to do and are good at) when there are people who are clearly the best in the business at teaching their subject matter whose work we should be using instead.