If JMU and MSU both accept and push the SBC to 13 in football, could UMass be #14, at least temporarily? This could be the Minutemen's conference schedule:

Idaho (fixed crossover)
Appalachian State
@James Madison
@Georgia Southern
Georgia State
@Troy
South Alabama
@Missouri State

The home/away designations swap the next year, but would essentially be only for two years if the plan is to expel Idaho and UMass after the 2017 season.

In 2018, the worst case is both schools are independent, but they can play each other the first week of December.