If bandits would be simply allowed to transmit their gold around, many stories could be made, many would have motivations to do something.
Right now, bandit game can only annoy one side or another.
If they attack weak ones, weaklings are depressed very much, but bandits have no much fun.
If they attacks strong realm, that can make good training for realm's warriors, but again bandits themselves have little incentive. When playing bandit I feel as if it is expected from me to annoy other players, which is not my desire at all.
Nothing to offer, nothing to receive - how to reach interaction? One mechanically simple measure, allow them to hand gold, and I am pretty sure bandit game can become even interesting!