Not sure how that would work on the main thoroughfares....but a good idea.
I mentioned on a different thread that I had worked on a mayoral campaign several years ago. Campaign signs aren’t cheap, especially the larger ones.
So when our signs started disappearing we changed strategies a bit. We replaced the smaller signs - but only in higher visibility areas. The idea was that opportunists take advantage of the chance to destroy, but not so much when they can be seen and caught. We still had signs stolen or destroyed but at a smaller pace.
For the larger ones we embedded GPS trackers. We could then track one if (when) stolen. We caught the husband of our opponent red-handed with the sign still in the bed of his truck. Unfortunately our candidate declined to sign a complaint and the whole matter was dropped (and our guy lost).
In order for it to work you have to monitor the signs which means all night shifts sitting in your car and watching the computer screen. You also have to be willing to confront someone when they steal your sign.