#2 choice is another Penn State on the east end of the conference. Rutgers ? Not as big as PSU, not as well established athletically. Syracuse ? Not so much recent success, although basketball pretty competitive, football is lagging. West Virginia ? Athletically successful, you'd own West Virginia, but that's just not that many TV sets. Missouri's profile is similar to West Virginia with more TV sets.
At some point, Notre Dame
One thing to keep in mind is the Big Ten Network. The Big Ten now must review any proposed member's ability to bring additional paying subscribers to the network. In most of the Big Ten territory, there is only one RSN, making it ripe for the Big Ten Network to step in as a second RSN. Contrast this to New York state and northern NJ, where cable systems are already picking up FOUR RSN's at $2/month each. In those areas, the Big Ten Network would almost certainly be limited to being part of a premium sports package with limited subscribership. Adding Rutgers or Syracuse, who I've always thought would be great additions to the Big Ten, would likely therefore add only a limited number of tv homes for the Big Ten Network, i.e. those purchasing a premium sports package.
Missouri, on the other hand, could bring over 2 million additional TV homes, which could be leveraged onto basic tier at $1/month, for a potential $20-25 million per year incrementally to the network.
One thing Notre Dame could bring is helping the conference pick up premium subscribers outside of the Big Ten core region. Like SU or RU, this would include NY/NJ, but also would cover the rest of the country. Not sure the combined value of ND and the Big Ten would actually be greater than the current separate arrangements though, i.e. not worth the bother.
Frankly, with the Big Ten Network, Missouri now looks like the Big Ten's best choice if they were interested. Rutgers may be able to deliver basic cable clearance in NJ even with 4 other networks. If so, this would provide a few million homes. Finally, another decent choice would be Maryland, who might be able to bring 2-3 million TV homes.