Making the AI smarter as you go up in level is exactly the same as having an incredible AI to start with and making it dumber as you go down in level.
Unfortunately, Civ AI doesn't work quite like chess. The right algorithms themselves haven't been discovered yet, so making an AI stupider or smarter is more a matter of swapping out algorithms than tuning parameters. A Chess AI can be made stupid by allowing it to look only one move ahead -- there's nothing comparable for a Civ AI currently.
Unfortunately, Civ AI doesn't work quite like chess. The right algorithms themselves haven't been discovered yet, so making an AI stupider or smarter is more a matter of swapping out algorithms than tuning parameters. A Chess AI can be made stupid by allowing it to look only one move ahead -- there's nothing comparable for a Civ AI currently.