A team that has Peyton Manning under center at quarterback can run itself offensively. What the Colts need to do is hire a head coach who is a defensive guru, and has experience with both building a unit and turning one around immediately.
The person that comes to mind for this position is Gregg Williams. He's had top defenses with the Titans, Bills, Redskins and Saints, and has come into the last two stops and immediately turned a bottom rung defense into a top 10 unit in his first season.
He's had a couple years under both Joe Gibbs and Sean Payton, who are renowned offensive play callers. That should have helped him get a feel for the offensive game more, but in the end, he just needs to hire someone that Manning can get a long with and just be along for the ride.