I have been interested in incorporating MG's into our program as garden coaches. This idea has yet to catch, however it could be a great way for MG's to spread their wealth of knowledge.
Garden coaches would visit with each school's garden leadership once every two weeks during the growing season. They give tips for what to plant, are you watering enough, is your compost functioning, and general recommendations on what is needed to maintain a thriving garden.
I currently do this for 10 schools in my district. However, I am not a master gardener.