Tracks:
-Monaco - Real Life
-Twing Ring Motegi - Real Life
-Silverstone - Real Life
-Tokyo R246 - Fictional based on Real Life
-Grand Valley Speedway - Fictional
-Indianapolis - Real Life
-Pikes Peak - Real Life
Cars:
-Alfa Romeo Giulia GTA - '1965 Road Car
-Aston Martin Valkyrie - '2017 Road Car
-Audi Quattro - '1980 Road Car
-Audi R8 Race Car - '2001 Race Car - One of the most successful Le Mans winners.
-Audi R10 TDi - '2006 Race Car - First diesel car to win Le Mans.
-BMW i8 - '2015 Road Car
-BMW M1 - '1978 Road Car
-BMW M3 E36 - '1992 Road Car
-BMW M3 GTR Race Car - '2001 Race Car - A fan favourite of many (not because of Gran Turismo though).
-BMW M3 G80 - '2020 Road Car
-BMW M5 E39 - '1998 Road Car
-BMW M5 E60 - '2005 Road Car
-BMW M8 F92 Competition - '2020 Road Car
-BMW V12 LMR - '1999 Race Car - The car that beat the Toyota TS020 at Le Mans in 1999.
-Bugatti EB110 - '1992 Road Car
-Citroen C4 WRC - '2010 Race Car - The car driven by the legendary Sebastian Loeb that gave him the most success.
-Chaparral 2D - '1966 Race Car
-Chevrolet Covertte C1 - '1953 Road Car
-Chevrolet Corvette C8 - '2020 Road Car
-Chevrolet Corvette C5R -'2000 Race Car
-Dodge Viper GTS-R Team Oreca Race Car - '2000 Race Car - A Gran Turismo icon for many in the past games.
-Ferrari 488 GT3 - '2016 Race Car
-Ferrari F2004 - '2004 Race Car - The F1 car that gave Michael Schumacher his 7th and last championship.
-Ferrari F355 Berlinetta - '1994 Road Car
-Ferrari SF90 Stradale - '2019 Road Car
-Ford Fiesta WRC - '2017 Race Car - Winner of both constructors and drivers championship in 2017.
-Ford GT40 Mk.1 Race Car - '1965 Race Car - The car that beat Ferrari at Le Mans.
-Ford Model T - '1908 Road Car
-Ford RS200 Rally Car - ' 1985 Race Car
-Honda Civic Type-R EP3 - '2001 Road Car
-Honda HSV-010 GT500 - '2011 Race Car
-Jaguar XJ220 - '1992 Road Car
-Lamborghini Gallardo LP560-4 - '2009 Road Car
-Lancia 037 - '1983 Race Car - Last mid-engine rear-wheel drive car to win the WRC.
-Lancia Delta HF Group A - '1987 Race Car - The most successful Rally Car of all time, an icon of Rally pretty much.
-Lancia Delta S4 - '1985 Race Car - The car that dictated the death of Group B. A Legendary Group B Car.
-Lexus LFA - '2010 Road Car
-Maserati MC12 - '2005 Road Car
-McLaren 765LT - '2018 Road Car
-McLaren P1 - '2014 Road Car
-McLaren Senna - '2018 Road Car
-Mercedes 190 E 2.5 16V Evolution II Road Car
-Mercedes 300 SLR - '1955 Road Car
-Mercedes-AMG W11 EQ Performance - '2020 Race Car - The F1 car that gave Lewis Hamilton his 7th title to equal M. Schumacher as well as the fastest to date F1 car in the history of the sport.
-Mitsubishi Lancer Evolution I - '1992 Road Car
-Mitsubishi Lancer Evolution VIII - '2003 Road Car
-Pagani Zonda C12S - '2002 Road Car
-Peugeot 905B Evo - '1991 Race Car - 1992 Le Mans winner
-Porsche 718 Cayman GT4 - '2021 Road Car
-Porsche 911 GT3 (992) - '2021 Road Car
-Porsche 918 Spyder - '2015 Road Car
-Porsche 959 - '1986 Road Car
-Red Bull X2010 - '2010 Prototype Race Car - The "what if we built a car with no regulations implemented into it" car. A Gran Turismo exclusive car.
-Renault 5 Maxi Turbo - '1985 Race Car
-Subaru Impreza Group A - '1995 Race Car - Colin McRae's WRC championship winning car in 1995.
-Suzuki Escudo Dirt Trial Car - '1998 Race Car - THE Gran Turismo icon car.
-Toyota TS020 GT-One - '1999 Race Car - A car that would've won Le Mans in 1999 if not for a puncture in the last 10 minutes of the race. One of the most beautiful race cars ever made and an icon among Gran Turismo fans from the past games.
I don't think I've asked for much did I? Even if 2 or 3 of these cars are pretty much "only in dreams" (the F1 cars). Outside of those, I think all the others can be updated into the game.
Outside of these I specifically named, a new addition of GT500 and GT4/GT3 cars would be good, as those are pretty much the core of racing pretty much.
A few Lotus and Opel would also be great, but the brands aren't even in the game... Same goes for Koenigseggs, but PD has never been one to put road cars with way over 1000 hp in the game, probably because of "balance" issues as these cars would be way too OP for road car races, they would be in a no man's land pretty much, but I would be delightful just to have the CCX and the regular Agera in the game, those 2 are 800-900 hp cars respectively and are iconic in the supercar/hypercar world, certainly would have their place in the game.