Automating is just as bad as it sounds. It is not matter of finding what is the best improvment for a tile. Sometimes you have to be dynamic in your improvment. That is an important part of the game. You need the less land if you use it effectively. Let me give you an example how a dynamic improvment works. Suppose you have a city with 10 tiles and this city is good for financinal thing. Now you can just do cotage in all tiles, but what is the point on doing that, you have to wait very long that your city reaches to the right population. You can either irrigate all the tiles to populate your city as fast as possible and then change all those tiles to cotage. Which one is better?, you have to think about it. In another hand I never cottage those tiles near the border and many other things you should take in account.