Take the ATS coupe, make it less stylish with a more spartan interior. Only offer it in black and put a Buick badge on it. A tuned version of the CTS Vsport's V6 turbo, the Corvette's 7MT with a short final drive and long 7th gear for a high potential top speed. The top end punch of the V6 turbo combined with the 7th gear ratio could make it the fastest production American car again. Make it look sinister in the front fascia and compare it to Darth Vader.