Maybe I am missing something, but if my wheel is set at 900 degrees in its control panel and I want rFactor to control the lock with the option in its control panel, should not the full turning range of my in-game car happen within the range of its own setting?
No matter what I do, the in-game car uses the range of my wheel (Fanatec GT2). For the existing cars, a setting of 540 closely mimics the actual lock, but that's not the point. Going forward, it should auto-adjust so when you switch from go-kart to 60's American sedan, you get the appropriate steering as log as it is not outside (higher than) the setting of your wheel.
Hopefully this is another temporarily offline feature to be addressed.