This is a great move. In the two game stores the collective of GMs I work with play out of, we have had an increased showing of youthful PCs(13 and under). We GMs had plotted amount ourselves about setting this very idea as a 'house' rule at our table to help with not only the cost(I didn't have much money just sitting on my dresser to have fun with at 13) but to easy them into the larger world of PFS. And now allowing us a second run at scenarios in 'core' mode is just the cherry on top. Fantastic work!!!