text: From what I've seen, almost every "complex" intersection in the city is done the way this one is, resulting in the same issues. I think what you suggest is generally better for anything but simple intersections where a single road crosses another single road. The actual physical signals are almost invariably as you suggest, except that they are on the "far" side instead of the "near" side (the latter being the right way for the map).
  You will also find that almost no intersections have turn restrictions that prevent U-turns. It will be a huge amount of work to fix these things.