Since Minecraft is very possibly a post-apoc game, I have the idea to add npc raiders into hard mode. The would almost always spawn with random armor and always have bows or swords. They would travel in groups and be hostile to hostile mobs and golems. They would also raid and kill villagers and players. The AI would be very difficult, but this is just an idea. They could probably start off as re-shaped Skellies and Wither Skellies. They would steal from chests, and if there was armor or swords in it, they would equip it.