Simce it is possible that between 1 and 3 teams relegate from each Big 8 conference, and between 0 and 1 promote, it would be impossible to maintain conferences.
For example, relegation from D.II will involve between 4 and 12 teams from each conference, and promotion from D.III will involve between 0 and 16 teams from each conference.
If 7 Big 8 teams go up amd 11 come down, how do you decide which 4 don't? And then you have to consider whether it is important to try to do as many as possible.