That was basically how Alpine Gearing worked but advances in the past couple of decades have eliminated the need to do that. Alpine Gearing had 3 front gears with two larger rings nearly the same size. The limited rear gears made this set up useful, however, with the increase of rear gears the need to have a half step difference front chain-rings disappeared. Now you can just change the rear gears for most changes and change the front for a more drastic change.