In a 15 team ACC, an 8 game conference schedule will be kept. The reason is that 4 ACC members (Clemson, FSU, GT, Louisville) end their seasons Thanksgiving weekend against an in-state rival in the SEC. That means they only have 3 games to schedule each year. None of them will want to go to 9 ACC games.
In a 15 team league, you must play without divisions, like this year. That means, first, that any chance of a team losing the playoff because of losing the CCG to a team with 3 or 4 losses is gone. The two best teams always will meet in the CCG.
It also means that nobody will play 7 ACC teams every year. Everybody will play everybody often. The best plan would be to have each team have 2 annual rivals. That means that there will be 12 teams left to play. Those teams can be divided into two groups of 6. Each of those groups will be played twice every four seasons. So, everybody will play 2 teams every year and 12 teams twice over every four year period.
That leaves everybody with 4 OOC games per year. ND-SC is the largest and most important inter-sectional rivalry in the sport. It must be maintained, including the way it has been played (in Oct when in South Bend and Thanksgiving weekend when in LA) - assuming that the Pac will continue to allow that scheduling.
Navy is most important to ND football because Navy will play ND anywhere. ND football has no need to ever play teams from anywhere if ND can play periodic neutral site games in those regions/states. In other words, ND needs to play in TX every few years, but ND has no need to play either Longhorns or Aggies, nor Horned Frogs nor Bears. ND can meet its TX needs by playing Navy in Houston.
Stanford is not the same as SC and Navy, the two teams that ND has played most. Stanford is a recent rival, created as such to have a game to end the season in 'warm' weather in the years when SC plays at ND in Oct. So Stanford is not a Must Keep Annual Game as SC and Navy are. What Stanford provides (ending every season away from Sound Bend in good weather and playing in CA other than LA) can be provided in other ways.
The game has changed a great deal since ND last won a National Championship - 1988. I am among a large, and growing, group that says that ND cannot win a National Championship in football now unless it becomes a full conference member and gets in the habit of fighting to win a conference championship.
If any of you think that the worst can't happen, that this streak of more than 30 years of no ND National Championship can't continue much longer and that ND cannot lose any more status, should ponder how the nation would respond to UNC fans chirping about being a unique blueblood if our last basketball National Championship came in 1988.
If you cannot give up things that are not truly essential to your ability to reach greatness in order to avoid nearly worst case scenarios, then you are part and parcel of the bad that continues.