First off I love LFS and have played it for at least 4 hrs a week for the last 18 months. The #1 thing that would make it the best sim in the world would be to have tons of real tracks. As a racer in real life I dream of the day I could sit down at my computer and learn new tracks before I show up to them. Since I am from the US these would include:
Road Courses:
Road America, Mid Ohio Sports car complex, Blackhawk Farms, Gingerman Raceway, Grattan, Putnam Park, Road Atlanta, Virginia International Raceway, Roebling Road Raceway, Carolina Motorsports Park, Barber Motorsports Park
Oval w/ infield road course combined:
Indianapolis, Milwaukee Mile, Gateway International Raceway, Iowa Speedway, Daytona, New Hampshire International Speedway
Road Courses:
Road America, Mid Ohio Sports car complex, Blackhawk Farms, Gingerman Raceway, Grattan, Putnam Park, Road Atlanta, Virginia International Raceway, Roebling Road Raceway, Carolina Motorsports Park, Barber Motorsports Park
Oval w/ infield road course combined:
Indianapolis, Milwaukee Mile, Gateway International Raceway, Iowa Speedway, Daytona, New Hampshire International Speedway