Would also be good to get back : unmaintained houses. If you have a place that you didn't visit in a while, grass started to grow out of the floor, walls start to break, etc ...
I like the idea of using neglected houses as models or blueprints, since I play in creative mode and sometimes I have to generate my landscape, and a ruin like that doesn't necessarily fit in. If these houses were available as blueprints, you could place them anywhere you like. I find the idea of being able to convert such ruins very interesting; perhaps three models of them.