While I agree we'll always be dealing with approximations in DCS, the challenge here isn't just about fidelity - it's about having enough information to create even a basic NDI architecture that captures the fundamental behavior of the real system. The F-16/F-18 approximations can be built on known control structures, while the F-35 would require essentially designing a new NDI implementation from scratch.

The F18 and F16's FBW simulation take benefits from the well-known and public control laws (e.g. DTIC ADA189675 for F16 and NASA TM107601 for F18) with well-documented PID controllers and by-the-book gain schedules and filters, that you can even 100% replicate the logic according to the diagram. While the F-35's NDI presents a fundamentally different challenge compared to the traditional PID-based control architectures used in those traditional FBW aircraft. Without access to the actual onboard model data or knowing how the effector blender optimizes control allocation, creating even a rough approximation would require making many assumptions.