Bound/Shackled Zombies and skeletons

A new varient of the Zombie and skeleton called the Bound or Shackled Zombie/Skeleton could spawn in dungeons. They would be chained to walls in the prison cells. They could spawn with a hook attached to a wall, or these hooks can generate with the structure, and the chains spawn, connecting to the walls. As they are chained they cannot move too far from the wall. The skeletons would spawn without weapons, as they would not have them when they died. I assume this would be easy to add, as skeletons and zombies exist in game, as do leads. This should give an easy foundation for the addition of these new mob varients.