I didn't know why the Pac-12 decided not to go into that deal - I just knew that it was tried and failed before it started.
And that's just one of the reasons the B10-SEC challenge would never work. (Though give a couple of teams credit - SOME credit, anyway. Isn't LSU playing in Wisconsin this year - maybe not Madison, WI, but the state of Wisconsin.) But you're right - the SEC is notorious for not leaving their region. And I can't say I blame them - screw national perception - if you're known as the "best conference on this side of the Kuiper Belt", why risk more than you have to gain? Anyway, I digress. Note that my plan was to get Big Ten teams to the south for the first game of the year. Scheduling all 14 teams to do that would be tough, especially with a 9-game conference schedule coming up. Half the teams will already have 5 away games. They can't afford to have any more away games. So you split the teams up so 7 games are at the end of the year in Big Ten stadiums and 7 games are at the beginning of the year in SEC stadiums. The teams that play 5 conference away games play the SEC at home, and the teams that play only 4 conference away games play the SEC on the road. That pretty much eats up EVERY team's away games every year. They have no more flexibility in scheduling who they want. They already only have 3 choices, and this game takes 1 away. They need to play 2 home games. They can't schedule a home-away series with anyone else. I know some teams have out-of-conference rivals. Iowa-Iowa State, Michigan State-Notre Dame, etc. Those will no longer be possible. So the Big Ten will be against this set-up. Then there's the whole "play in the Big Ten stadiums the last week of the season - AFTER the conference championship games" thing. Do they move the conference championship game up a week, or get permission from the NCAA to play a week later than they're supposed to? Plus, there's the whole thing where the SEC wouldn't gain anything from playing in the cold - if they win then they're still the best conference, and if they lose then maybe questions are asked about that.
As to your third point, if the SEC isn't enough to pull teams away from their historical out-of-conference rivalries, the ACC or Big-12 wouldn't be, either. I just thought it would be cool to see a conference vs. conference challenge. It wouldn't work, though.