Would be very cool and more realistic if some npcs had the behaviour of construct and repair their home, beeing able to expand it, creating new houses and things like that. So when you return to an city, it might be a bit different, as it should. Since the game alredy make random planets, pehaps there would be an easy way to use this function to randomly remake and/or expand a small part of the citys/houses every time you come back to it, according to time you was gone.