I think a really neat addition to the game would be stairs. Perhaps have a slope range that could be built on using a hammer, just like floors. The stairs could make going up and down slope the same speed as normal. Different types of material could be used such as rock, stone, and wood. Then you could add a few more Border Tile types, such as hand-rails for the stairs in wood or iron. This would make an excellent cosmetic change, and could really spruce up the exterior of houses and settlements. I don't think it would work well inside a house due to the length-height ratio and the size of the average home. But outside it could make a huge difference. I am unsure what the skill level should be in though. Carpentry/masonry/paving.