The real-time weather is a great way to get realistically varying weather, especially for long races. It's coming directly from the actual weather in the actual location. If anything, it's a cheat, since they don't have to get the simulation quite so accurate.
The changeable weather wasn't a gimmick in GT5, because of how it affected races (esp. online), but it was lacking in fineness of the range of situations it could "land" on through the simulation. This is apparently difficult for PD to fix, so this real-weather "cheat" is a potential improvement.
As for the "star aligment", I think the reason they're modeling latitude and longitude effects is more to make sure the sun comes up at the right time and in the right place for 24hr races etc. which is a nice touch of authenticity that's easy to do. Plus the "quality" and colour of light is very different as a result of these changes in planetary / celestial geometry, which is not so easy.
Actually, the whole lighting of a scene during daytime is dependent on these little changes, and will make the real circuits more like their real-world counterparts, although it's also dependent on the seasons.