Maybe there could be a structure that has a chance to spawn in Sabaody biomes that are like Sabaody park that spawn an enemy known as "Slavers," and these enemies attempt to knock you down and cuff you instead of kill you, and possibly try to carry you and lock you up as well. It'd probably be pretty hard to add but could add to the exploration of the world. And maybe the building could spawn villagers in cells somewhere to add a bit more to the structure.