First of all, yes I DO know that there are other threads about this and that Dinnerbone has a similar idea. I was not aware of it when I made this thread. Please still take a look at my designs!
A simple idea, but one that I think would be really cool for the game. I think witches should spawn in solitary huts in swamp biomes, where they live a hermit-like lifestyle and brew potions. The little huts should generate (very rarely, since they have a lot of materials) with cauldrons and occasionally brewing stands. I think witch huts could add some spice to a currently rather boring biome.
Above: A fence around the house would fit the witch's solitary lifestyle.
Above: The interior of the house, with a cauldron, brewing stand, and chest.
Above: Note the erratic placement of redstone torches for lighting.
Above: The chest would contain brewing supplies and rarely finished potions.
Above: The pointed roof is made to look similar to a witch hat. The shape was inspired by the Baba Yaga house in "Bartok the Magnificent."
Above: There would have to be a way for the witch to always stay in or near the house.
Remember to thumb up this post if you like the idea!