As much as I loathe the idea of replacing the brake cable because the swaged end is mangled, I think it's the right thing to do (and I work in a bike shop that specializes in used bicycles and vintage repair, I'm not one of the new breed who can;t overhaul a 3-speed hub). It's a very inexpensive part, five bucks tops; and the old brake cable is of course re-purposeable for any number of things.
There is nothing on a bicycle that's complicated. Almost every single part can be overhauled or rebuilt.