The only reason Idaho moved to the FBS was because refusing to do so would be an admission that in-state rival Boise State was better. The financial support in the state would shift. 10+ years later, and that happened anyway. Its all down to pride now. They'll keep this charade going even if it kills them. Independence? Really? That approach is rough for schools who have the resources. They simply don't have the resources or want-to in order to be FBS.
The crazy thing is, the Vandals wouldn't even be in the top tier of Big Sky schools. Some of their fans see them as a very inferior conference, yet I'd like my chances with Montana, Montana State, Eastern Washington (Happen to play this Thursday), Portland State, etc. They want badly into the MWC, yet I'm not sure they would even perform at a high level in the BSC. Where is the incentive for the MWC? They gain the Spokane market? Are you shittin' me? Spokane is owned by WSU alums.
The logical and correct thing to do is return to the Big Sky. That's not the way this will end though....
Bottom line: the Palouse is barely grounds for one FBS school, let alone a second. Its the equivalent of there being a school 8 miles from Laramie.