Cars are routinely given power restrictions under BOP regulations. A restriction to 20% is a bit excessive mind, but you'll note it was speculative: There have been some very odd GT3 cars indeed over the years - like the Cadillac ATS or Morgan Aero 8. After all, there's very little left of the original car besides some of the body frame. I've tried playing a racing game with my feet. It isn't easy.