Right now this property is read-only, and there is no native to set it.
According to @nihonium, it requires (at a minimum) writing to the same memory address that you guys get the value from, but may also require more effort to get it working.
Vehicle.SteeringScale is get/set, but it (and the “SET_VEHICLE_STEER_BIAS” native) only seems to work with a player/ped in the vehicle.
If this could be looked at for a future release, that would be appreciated.
Thanks!