I think a great addition to the B1G would be Mizzou and KU. I have Mizzou more than any of our current rivals so I'd love to see us play them again. KU has hoops and is AAU.
I don't think Iowa State is a great addition. B1G is going to be looking at $$$ and they don't bring a TV market. KU and Mizzou would bring KC and STL. Might be tough to convince Mizzou to leave the SEC, though.
Best case scenario for the B1G would be ND and KU out of this, imo. That being said my dream would be OU and Mizzou to the B1G.