I think the ideal, post UT/OU scenario for the Big 12 and ISU is to pilfer AZ and AZ State from Pac 12, possibly add BYU and Houston. Spanning 3 time zones is not great, but would have the same problem joining a PAC 16 "super conference". This approach brings in two more Power 5 schools covering a rich recruiting footprint. BYU would bring some national cachet; Houston is in the middle of talent-laden recruiting grounds and a large TV market.
Joining Big 10 wouldn't be all that bad. Would have the cultural, academic and geographical fit. Plus, Cyclones' recruiting is not dependent on Texas pipeline. Regularly playing Wisconsin and Nebby (and occasionally tOSU, Mich, Sparty and Penn State) could be interesting. Besides, from a culture and scheme point of view, Iowa State kinda' is a Big 10 football program.
Joining the PAC 12 is far from ideal. It is a loooong trip for a lot of away games and who watches or cares about PAC 12 football anymore? Their per school TV revenue is worst of the Power 5.
Whatever happens, Iowa State has set itself up as well as could be expected: Rising, Top 10 football program with sustainable success, durable culture, academic excellence, big investments in facilities. A lot of other Big 12 and Power 5 schools are not as well positioned for another conference realignment missile crisis.