I think the editor is your only option. That does limit you to no Team Builder and offline only. The conference scheduling logic is hard coded into the game. I believe this to be correct for the scheduling logic (I copy & pasted it from another thread):
For 8 or 9 conference games, use this info:
4-8 schools – 7 conference games. There are no protected rivals since everyone plays everyone else. For conferences of 4-6 schools FCS opponents will play the part of your additional conference games
9 schools – 8 conference games. There are no protected rivals since everyone plays everyone else.
10 schools – 9 conference games. There are no protected rivals since everyone plays everyone else.
11 schools – 8 conference games with a rotation of other conference members.
12 schools – 8 conference games when using protected rivals. 9 conference games when not using protected rivals. (Note: C-USA will use their 8 conference game, no protected rival format by default)
13 schools – 8 conference games. Protected Rivals are not available in conferences with odd numbered schools.
14 schools - 8 conference games when using protected rivals. 9 conference games when not using protected rivals.
15 schools – 10 conference games. Depending on the rotation you will have 6-7 division games in a year with 3-4 rotating cross divisional games (based on the MAC's 13 school schedule rotation)
16 schools – 9 conference games. With protected rivals you will have 7 division games, 1 protected rival, and 1 rotating cross division opponent. Without protected rivals you will have 7 division games and 2 rotating cross division games.