I'd love to have spiral staircases as well as ladders. No, I wouldn't just love them, I need them.
For example, I tried adding a roof balcony (or whatever it's called if you can walk around on one part of the roof as it's flat) to the small house at the end of the BFFs' street. Nearly impossible. After breaking my fingers twice in the process I managed to place the stairs at the river-side end of the house, which basically made the parents' bedroom a third smaller. But at least it worked and now they've got a telescope on the roof, which wouldn't fit into the "garden" area.