Better buildings

I REALLY miss the possibility to add more complexity to buildings like walls, lockable doors, windows, rooms, furniture–not to mention multiple levels. I am now trying to add a secret basement to this church I’m building, but can’t seem to find a logical way to do it. I first started out adding a POI with a map of both the main level and the basement but quickly realized that the monster I’m planning to lock in the basement would just jump over to the main level because there are no walls keeping it there. It won’t be a secret basement either as it shows up on the initial map. I guess I could make it hidden as part of a quest, but then we are back to it going through walls again, and I have no way to add entrances/exits either. This seems like such a basic feature so I’m wondering why it’s not been added?