Dungeon upgrades

Dungeons have been untouched ever since Dungeons were introduced. The only monsters that SPAWN in these dungeons are zombies, skeletons and spiders. Why don't you have bigger dungeons that are harder to get past and contain more loot? There could be different dungeon types depending on what biome you are in. These dungeons will keep the same look and have more mob variety to spawn from. For example: You will be able to find Witch spawners in Swamp biomes.