Nice idea however the thieves want the cord for the copper not to take home and use on their RV.They will simply cut the cord and take it. The thieves don't care about salvaging the cord. . A thief will cut the cord at the camper and take the entire cord and extension cord.
Consider many RV's including mine, have a twist lock connection at the RV that can be just removed and taken. Our RV cords are very expensive and vulnerable to theft
I like the idea but unfortunately your lock will likely not deter a harden low life thief with cutters.Trying to protect the cord is futile.