Regarding the overall direction:
Although titles like TXR and Forza are also set in Japan, I don’t think it’s necessary to compete with them head-on. Since “JDM: Japanese Drift Master” is described as a tribute to Japanese street racing culture and drifting, I would love to see a deeper focus on Japan’s car culture—especially from the 1980s to the 2000s, when many of these cars were actually sold and actively driven.
If that era isn’t fully familiar, I would strongly encourage consulting with Japanese enthusiasts. There is a wealth of reference material available—for example, searching “90年代 峠”or"90年代 走り屋" on YouTube gives a good sense of the atmosphere. There are also archived issues and videos from Video Option and Hot Version, which show not only what kinds of cars were popular, but also how they were modified and the overall mood of the scene.
From a Japanese perspective, period-correct styling would likely fit the game’s world better than modern widebody kits like Pandem or Rocket Bunny. It would also be great to have aero options that allow players to recreate cars similar to those seen in works like Initial D.
One more thing: your passion for Japan really comes through. With that in mind, I think it would be wonderful if you could also include elements that pay homage to racing games from the PS1/PS2 era and arcade titles. Those games have a unique atmosphere that modern racing games often lack, and many fans are still hoping for spiritual successors. If possible, I’d love to see subtle nods to those classics reflected in the car roster, customization options, and rival cars.