GT style shells that are connected to a roll cage and have replaceable panels.
Bead-lock wheels for touring cars
Touring car racing has declined because it has got too nerdy and expensive. The aerodynamic mazda 6 shells and dish wheels are ugly. Lets not forget the amount you have to spend on tires and all the other stuff to make your alien ship of a car competitive.
Classes like USGT and VTA are fun in my opinion. More focus on drivers skill then tires and setup