This is an awesome and gorgeous track, I feel I have to give it 5 stars because of how solid it is and the nostalgia from playing GT back in the day, but there are a few issues:
The most impactful is the AI not coming out of the pits, I always test-drive tracks in a TrackDay setup and only for Grindelwald-C Roadcourse can they come out of the pits. All the other layouts they just sit there.
I believe it's because the pitline does not end close enough to the racing line, the AI doesn't see a connection, and so it doesn't even try. I was able to fix this on Course-B Long by making my own pitline with the AI-Tool that ends as close to the racing line as possible. I also brought the pitline a little closer to the pits to make sure they could "see" it.
The other "issues" I found are very minor: (1) with a full grid and all cars in the pits (except Course-C), an AI always spawns in the same pit as my car so there's an overlap. It's not a huge deal obviously because of noclipping, but also not ideal for immersion's sake. (2) I just wish there were more tire-marks in the corners to show the racing line, as beautiful as the track is, I think that would help elevate it even more.
Seriously a great track! I'll be making new pitlines for all the layouts and having a lot of trackday fun with it for sure! And looking forward to further iterations.