If I could start over, I would build only 1 road and place all of my caravans on it. When attacking, the caravans drop all of their gold as soon as your first troop is deployed. Sometimes you can run down the initial 30 seconds (when inspecting a base) and wait for the caravans to move to a spot that is out of range of most defenses. You can place an isolated road in the middle of all of your defenses and move all the caravans to that one road segment, but they eventually wander to other roads. Caravans prefer to stay on a road but can still move between disconnected roads and, when attacked, they will drop their gold wherever they are, even if it's not on a road!
However, it is too late for me to try this and I'd be interested if anyone else has. The downside is that you don't get gold from a road network, but the upside is that the gold accumulated from your caravans is better protected...