They should take 6 right now. BYU, Cincy, UCF, Houston, Memphis, and Boise. Cap the strongest G5 at the knees and
Establish themselves as the unquestioned 5th best football league with the stated goal to overtake the pac12. At that point, the gap between the big12 and the next best league would be much larger than the gap between the big12 and the SEC.
That league would immediately be better than the Pac12 in basketball which is not nothing. In fact, it would be the first step in overtaking the Pac12.
Supplanting the Pac12 in football would be a realistic goal.
This would build a vision that would galvanize the league. Taking it slow is just weak.