You gotta remember that this is a business deal; take the emotion out of it. It's the BYU administration's job to get the best conference deal they can, especially if they're going to stop being independent. It's the Big 12's job to integrate any new conference members while maintaining equitable treatment for current members.
If BYU gets too many "special demands" if they join, blame the Big 12, not BYU.
Ideally, the Big 12 would treat ALL members the same, regardless of their level of "significance."