BSU makes 10. I'd also love to grab up KU and KSU. Missouri would be a nice addition if they get left out of any expansion. But they are a little too far outside of the "MWC footprint" for my taste. The Kansas schools are pushing it as is. But if the MWC does expand past 10, then we need to push it to at least 14 IMO, in order to have a hope at renegotiating the current TV deal. And in order to assure BCS inclusion, we'd need to land some big players who have seen a lot of recent success.
Other choices could include Houston, Baylor, Tulsa, Fresno, definitely Texas Tech if they get left out in the cold of whatever expansion the rest of the Big XII South is a part of. UTEP would be a nice geographical fit but wouldn't bring a whole lot to the table.
I do worry that 14 or 16 is just too big. We've already seen it fail once. And I'm not sure even the "Big Pac" could make it work.