Apparently you missed the rest of my post. I'm well aware of the geography argument. But, if we're willing to join the MWC as a worst-case scenario, which has roughly the same geographic footprint as the Pac 1X, why shouldn't we be willing to join the Pac 1X when the money from that conference would be far greater than either the MWC or Big East, and it would put to bed the idea of ISU being left out of a BCS conference permanently? The Big East can't offer us that as it's just waiting to be picked apart by several conferences as well, and there's no guarantee that ISU would be going to one of those.
I read the rest of your argument, but the choices for ISU right now are not limited to the worst case MWC scenario and the the Pac-12.
The Big East can't offer Pac-12 money right this minute, but if a number of Big 12 teams joined the Big East, the next TV deal would likely be quite lucrative. And if the money is good and the power distribution is fairly equal, that conference would be stable, with better travel logistics. Why would anyone leave?
Just because OU wants to go to the Pac-12 doesn't mean it is the present best option for ISU.
If it is determined by ISU administrators that ISU could not sustain long-term membership in the Pac-12, then that option has to go down to the bottom, just above the options for non-AQ conferences, and ISU has to try and find something else, most likely with the Big East. How horrible would it be to turn down a Big East offer for the Pac-12, only to have to withdraw from the Pac-12 in five years?
On the other hand, If ISU thinks they can sustain long-term membership in the Pac-12 with no adverse effects on the AD or student athletes, then it would seem wise to further pursue a move to the Pac-12.