I'm fine if we can find a happy medium with JT, but let's also remember that the Colts only Super Bowl win during the Manning years did not include a JT type, Edgerrin James type runner. It was more of a 1,2 punch between Addai and Rhodes.. A running back has value but it's the easiest piece on the offense to replace without taking major bite out of the attack.
The QB, the OL, and the WR corps are more critical. Heck the Patriots never dish out big money at RB or WR. They only spend at QB and OL. I think a RBBC allows you to be more diverse and gives teams more tendencies to prepare for.