Sportscar GT 2
Start your career racing karts, then move to formula fords, formula 4, then gt4, then gt3 or gte. Then jump into prototypes. Go from racing at your local karting circuit to lemans in porsche prototypes. Throw in some single make classes (radicals, spec racer fords, legends). Use the sportscar gt as base idea what it is and make the career central part of the game. Have players earn money to buy upgrades, buy teams, buy rides. Innovate with the career concept and try to add new things into it (make testing interesting, add stuff like brand loyalty, try to create a factory driver/gentleman career path, make geography play a role as well so players can start from europe, usa or japan for example... etc...)
Make it good and release it. Develope and update the game for couple of years. It will be good proposition for sim racers because of the good rf2 physics engine and ai and simulation features. It will also be the de facto gt racing game with full rulesets for each series. At the same time it is a fresh take on the old school racing games everybody grew up with while also being its own thing.
Make some historical dlc. Vln dlc with nordschleife. Lemons dlc! Be open with the dlc and allow people race together with people who have no dlc cars. Try to avoid dlc tracks and focus on full series and cars. Add online functionality into the game so that people can create their own teams, leaderboards and events. Throw in some purely cosmetic mictrotransactions like skins, helmets and driver suits (both skins and models).
It can't fail!
(or make viper racing 2 but with ALL the sportscars)