There is a startup called Springboard that is working on something like that, although I do not understand all the details. I agree - that is an awesome idea - the domain here is restricted to MOOCs because it's closed form and standardized, where tutors can be recruited for their expertise in a given course. An apprenticeship requires, I think, a much broader approach to what constitutes a "match" between both parties, and the interactions would need to be facilitated in a completely different way.