I believe you are over thinking this. A. Foster and M. Forte have much more potential to produce than A. Bradshaw, who may be losing a a decent amount carries to B. Jacob as New York will be looking to really pound the ball against Carolina. I think T. Hightower will benefit from B. Wells injury, but don't think he has the ability to produce as much as your current starters.
I agree with Rabbit, but I would consider Hightower over Forte in both ppr and non ppr. With Martz, you never know how many times they are going to run the ball, and if they do he will be losing some carries to Chester Taylor, as well as going against the strength of the Lions defense, which I asssume will be their run defense (their d-line of Suh, Williams, Vandenbosch, and Avril should be able to do a better job of stopping the run than the secondary will of stopping the pass). With Beanie banged up, I think Hightower should have a field day against the Rams defense.