Very ingenious rig to prolong the life of the rudder line, Tony!
As far as having a coating on the wire such as Teflon, plastic, enamel.. and so on, it only helps for awhile but since the rubbing occur at the plastic edge, it will eventually start to protrude through the surface and slowly eat away at the braided line.
My only suggestion is to cut a piece of brass, copper, or any soft metal that is less corrosive to saltwater and bend it to conform the shape so it can take the friction away from the plastic edge. 1/4 copper water metal piping with the fitting might be the best option and spray Teflon inside since the inside is smooth and polish.
