If the B1G truly wanted Mizzou they should have taken them back when they would have crawled across broken glass for an invite. They made perfect sense as a B1G School then, and still do now. If the B1G is suddenly serious about adding them, I think they may need to overpay just to get them to consider the idea. Mizzou has found success in The SEC, and quite frankly there is no compelling reason for them to move.
I've always maintained that The Big 12 is the most vulnerable of The P5 Conferences, for a multitude of reasons. Those schools with better options will someday exercise them as others in the past had already done. Its not exactly going out on a limb to say that KU/OU would accept a B1G Offer. I believe that ESPN will act to protect the ACC, simply because they own it lock stock and barrel and are not in the business of watching their assets be devalued. All this analysis and I didn't even need to consult my "sources" to write it.
I think they did want them, but the timing was never right. Nebraska was, and still is the best choice. It just seems like the Big10 wanted to take things slowly and integrate Nebraska better than they did with PSU. They were only taking one at that time. It just happens that the SEC needed a partner with TAMU. Never had the opportunity to get them after Nebraska.
That being said, I find it hard to believe that Mizzou would bolt. I'm sure the academics would love it, but the investment they are making into the SEC just to change the course and leave would be ridiculous. Then again, Flugs never said they had interest in the Big10, just the Big10 had interest with Mizzou.
All of that being said, if Kansas and Oklahoma are in the picture, then Mizzou would be the perfect school to get. Built in rivalries with Kansas and Nebraska, along with renewing one with Illinois.
UConn and Mizzou now would give an additional team to either division if they stayed with two, or these pods if they went to four:
Pod A: Illinois, Missouri, Nebraska, and Iowa (with a protected Illinois/Northwestern crossover)
Pod B: Minnesota, Wisconsin, Northwestern, Purdue
Pod C: Michigan, MSU, OSU, Indiana (protected Indiana/Purdue crossover)
Pod D: PSU, Rutgers, UConn, Maryland
You would have to add two more teams if/when Oklahoma and Kansas are added, but you could cross that bridge when you come to it.