I'd like to see more Rally and ALMS racing. I'd also like to see a super sedan racing series (like what they have in Australia. Youtube it. The crashes are heroic.) pitting the G8 against the Charger against...whatever Ford comes up with for a large RWD sedan. That would go back to NASCAR's roots well. If Toyota really wanted to play I guess they could bring their Avalon.
Or there could be a super coupe series with the Camaro vs Mustang vs Challenger, and if Toyota wanted in well, they have the tC.
