Dyno has been suggested, and rubbished, before, as have the car parts. It would be nice to see the torque curves of the engines in game, but we don't need adjustable torque curves by however means, as the whole point of LFS is driver versus driver, not car versus car.
At this point someone usually mentions, without thinking, car setups making the cars different, and thus it not being driver versus driver, but the car setup merely allows a driver to exploit the car to his best potential, rather than simply making the car faster. So it's still driver versus driver assuming both have setups that allow them to get the most from their cars with their driving styles.