I think it'd be great to add this kind of feature, however my only concern with it is the people who go out of their way to make silly, obscene buildings. I've seen some pictures of stuff in Minecraft or things like Farmville that give people the chance to make the homes they want and they just go crazy with it. If SE monitored things like that, then the idea is great.

However this also adds the problem that what happens when you have so many character houses that eventually there's no room for monsters to roam around?

Again, I love the idea, I'm just worried about implementation.