Do we know anything about Circuit Experience? I think it's confirmed as being present in GT7, but do we know anything else? I was personally hoping that the cars we're assigned for each course has more to do with the actual course, and not so much just a bunch of Gr.3/Gr.4 cars. I think the only exception in GTS was the Porsche 919 being assigned to Le Mans.
For example, I could see the Aston Martin DB5 or the Jaguar E-Type being the assigned car for the Goodwood Circuit, with the Lexus RC F being the car for Fuji Speedway. But there could still be Gr.4/Gr.3 cars, like how the Ford GT LM (IMSA) could easily be the assigned car for the Daytona Road Course. Then there could even be some Gr.X cars, like the F1500T-A being the potential car for the 80's version of Monza.
But I suppose this proposed larger variety of assigned cars would depend on some factors. Would you still allow such a large range of cars to be available to drive - albeit within the limits of Circuit Experience - regardless of your progress? Would there be certain courses that use certain cars (e.g. Monza 80's with the F1500T-A) that would be locked behind certain benchmarks, like a certain level? Or could there be multiple levels for each course, each with a different vehicle? That last idea seems like it could easily get repetitive in practice.
Overall, I ultimately wouldn't really mind if we had to mostly stick with Gr.4/Gr.3 cars again for Circuit Experience, with the occasional Gr.1 car. I suppose this is also why in GTS, not all layouts are in Circuit Experience, such as the B and C layouts of Sardegna, as this would likely lead to a shortage of remaining racecars to assign.
So, here's my conclusion. We know Trial Mountain, Deep Forest, and Daytona are returning. I bet that for the last one, we'll specifically be going on the Road Course for Circuit Experience, and I bet the Ford GT LM (IMSA) will be our assigned car, leaving us to wonder what cars will be assigned to us on Trial Mountain and Deep Forest. We know at least several cars are coming to Gr.4 and Gr.3, respectively such as the Alfa Romeo 155 TI and the Audi R8 LMS Evo. Furthermore, in GTS, some Gr.4/Gr.3 cars were not used in Circuit Experience: the Aston Martin DBR9, the BMW M3 (E92) GT2, the Mazda RX-Vision GT3 Concept, the Porsche Cayman GT4 ClubSport, the Ferrari 458 Gr.4, the other BMW M6 GT3, and likely at least a few others I forgot.
Clearly, if GT7 continues the trend of mostly assigning Gr.4/Gr.3 cars in Circuit Experience, there are tons of tracks that could be added - both from prior GT games and new to the series, both originally-designed and real-world - without running the risk of re-using a certain model. And again, that's before we consider another course that could assign us a Gr.1 car, like we saw at the Circuit de la Sarthe in GTS. I definitely imagine that the JGTC-era Supra GT500 would be the assigned car for Trial Mountain, as the image of that car on that course seems very much an emblem of Gran Turismo. As for Deep Forest, I could see the Alfa Romeo 155 TI being the pick.
But as much as I like Gr.1, I also don't see much room for more Gr.1 cars in Circuit Experience - unless the Daytona Road Course has us use a Gr.1 instead of the much more appropriate Ford GT LM (IMSA). (Of course, since it's improbable that LMDh/LMH cars will be at GT7's launch, I could see the Cadillac or Acura DPi racers being appropriate assigned cars, too. That is, if they're added.) Furthermore, the usual circuits that would seem best for Gr.1 are already taken up in Circuit Experience by Gr.4/Gr.3 cars, such as Monza, Spa-Francorchamps, and Interlagos. The only possible real-world courses that could be added and also be good for Gr.1 cars - as they've been part of the WEC calendar - are Silverstone, Sebring, the Circuit of the Americas, and I think that'd be it. But besides from all this, I think mostly going for Gr.4/Gr.3 cars with the sole exception be the dirt courses and Le Mans would be the best approach, come to think of it. If more dirt/snow courses are added, I know there are plenty of Gr.B cars that could be assigned, not to mention the idea that more Gr.B cars could be coming to GT7, either at launch or in content updates; the Lancia 037 being a highly likely example of such an addition.
EDIT: Here are my picks for what cars I'd want to assign to some courses, if they're added:
Pikes Peak - Audi Sport Quattro S1 Pikes Peak '87
Grand Valley Speedway - Nissan Skyline GT-R (R34) GT500
Trial Mountain - Toyota Supra (A80) GT500
Silverstone - Aston Martin DBR9
Monaco - Mercedes-Benz SLS-AMG Gr.4
Cape Ring - BMW M3 (M92) GT2
Goodwood Hillclimb - McLaren F1 GTR '95
Deep Forest - Alfa Romeo 155 TI
Circuito di Roma - Ferrari 458 Gr.4
Monza '80s - Nissan R92CP
Brands Hatch '80s - Jaguar XJR-9
Chamonix - Peugeot RCZ Gr.B
Autumn Ring - Mazda RX-Vision GT3 Concept