It won't be as easy as the Sims, but the basics of a house should be manageable. Then it may be up to the modders to create the floral wallpapers and carpets that Sims is so great at. The officeblock might be even harder, the skyscraper doubly so.
I guess the hard things would be making sure it had the right physics - if you push a house, it won't tip over in one piece, the wall will collapse instead. I think once the destruction rules have been finalised (how something destroys something else(brick will be different to wood, etc)), houses will become easier at least to code.
