1) Nick Saban addicted/obsessed with winning, has built a machine that is the envy of all of college football
2) Sean Payton offensive genius, Super Bowl winning coach, history of taking a team from mediocre to the mountain top
3) Jim Harbaugh tough, winner, a rebuilder and probably driven to succeed out of spite and disdain for the rest of the NFC West.
4) Pete Carroll a winner, and not only would it strengthen the Rams but weaken the biggest obstacle to owning the NFC West.

2 & 4 might require compensation, 1 & 3 might not be interested but those would be my top 4 choices.

Honorable mention:
Todd Haley provided he keeps GW and Fassel but installs more discipline into the franchise. Offensive mind, head coaching experience.
or
Tom Coughlin the anti Fisher, discipline personified.