I'd rather they keep Benford than Hamlin at this point. Benford was a zone CB at nova and looked good filling in last year. Plus he has the potential upside of playing safety if needed.
Hamlin did well filling in, but it's safe to say he was limited, and that was before the injury. And I agree that he may not ever step back on the field, or be the same player if he does.
Keep Rapp as the primary safety backup along with Marlowe, and then get Benford some reps as 4th safety.