I think a great idea would be tiles that could be "destroyed"

For example, you could destroy a certain wall.
Some tiles could take more abuse than others.

If there was a house I did not like, I could reduce it to a pile of rubble...

Then at a set time, all destroyed tiles would reset themselves, and its back to normal.

This would be great for you Castle Ideas.
So far there has never been a way to force your way into something, this would be great for the RPing element.

That's what NPC scripting is for- anyone can make a tile like that already.