But the reason I want those is to have an 18-team basketball league and then for football split each conference into upper and lower divisions within the 18.

9 is a perfect number for football conference since you get 8 opponents.

This way you get 8 regional round robin champions for a tournament and you get a weekend of 8 relegation/promotion games. (champions of lower division vs loser of upper division)

The idea is was to have these conferences defined by geography and regions, but the way the TV deals have shaken out, that would take a lot of reshuffling at this point.