Cross-over schedules should be set up so that each of the Big 4 teams in each division play 2 times in 4 years. Then the Big 4 teams would play the other 3 teams in the other division twice in 6 years.
For example Wisconsin could have the following cross-over schedule
Year 1 : @OSU, MSU, @MD
Year2: @MSU, PSU, Rut
Year 3: @PSU, Mich, @Indy
Year 4: @Mich, OSU, MD
Year 5: @OSU, MSU, @Rut
Year 6: @MSU, PSU, Indy
Year 7: @PSU, Mich, @MD
Year 8 @Mich, OSU, Rut
Year 9 : @OSU, MSU, @Indy
Year 10: @MSU, PSU, MD
Year 11: @PSU, Mich, @Rut
Year 12 @Mich, OSU, Indy