I think Mauer's years as a .300 hitter are done. He should be moved toward the back of the lineup where Suzuki is hitting.
As others have pointed out, more balls will be caught in LF with Willingham's departure, no matter who plays out there. Also, a number of balls have been misplayed due to the extra padding on the outfield walls.
The newly padded walls should give the Twins a marginal home field advantage because the bounce is now difference from most other outfield walls. Also, the Twins need better fans. They should support this young, exciting team no matter what the record is.
The Twins now have the pitchers to compete in 2015. I would take Gibson, Nolasco, Milone, Pelfrey, May & Meyer and put them on notice that they have a 2 bad game limit. 2 bad games and they go to the bullpen and the next pitcher is brought in. This would be true for Hughes too if he starts out badly.
Molitor was supposed to help baserunning and bunting, and both have been terrible this year. I see no reason to continue Molitor's employment in 2015.