The fines are a separate matter as to what you eventually do with the vehicle. They need to be paid, regardless of what else you decide to do. As you say, you can return the vehicle to standard condition or have it engineered for the modifications you want and then have the defects cleared by having the car inspected. But if you decide to sell the vehicle, it can't be sold with current defects and while still registered. You can clear the defects and sell the vehicle with registration, or cancel the registration and then sell the car. In any case, there's no way you could obtain a roadworthy certificate with the defects you've listed so the simplest way to get rid of the car would be to cancel the registration and then sell the car.