AS+Sun Country assumes that AS wants a MSP hub for connecting traffic like everyone else does. I believe AS (and JetBlue) want to focus on their coastal hubs and fly to smaller Midwest airports direct. Bypassing those legacy hubs eliminates a lot of BS.

Thus, AS+JB would be a better match. They could each continue to focus on their hubs and flying to the Midwest. They could offer a huge amount of 1-stop itineraries from coast to coast without relying on a big hub in the middle. BOS/JFK/MCO/FLL-STL-SEA/PDX/SFO/LAX and you could replace STL with dozens of Midwest cities.

And for the Midwest based pax they could offer direct service to the big coastal city.