I agree, I would rather play our main non-conference game in a fertile recruiting area, or somewhere that fans that don't live near Lincoln can attend, or against a big-name program that we don't normally play. Oklahoma, Texas, and Texas A&M would fit the bill. KSU and ISU would be good in the sense that a lot of our fans could drive to the game, but otherwise there isn't much upside to playing them.
Plus, Iowa State plays Iowa every year in nonconference, I doubt they will want to play us as well.