The Panthers need to make a point to add a veteran with some range and catch radius like Robby Anderson or Demarcus Robinson. I can foresee the loss of another wide receiver currently on the roster followed by the addition of a fourth or fifth-round draftee to fill depth and possibly fix the punt/kick returner issue.
The Panthers typically keep five or six wide receivers on the final roster and let one hang around on the practice squad. This year they might create a stiff competition for five spots because they know McCaffrey can handle a bulk of the work as both a running back and receiver.
If the Panthers act quick enough with this free agent group they can create a squad of experienced wide receivers all below the age of thirty. As long as the line holds up the potential of the RPO (run, pass option) can be limitless.