Funny this came up. On another forum, we just discussed how maybe GM should consolidate to two brands--Chevy and Cadillac. It works for Nissan/Infiniti, Honda/Acura, and Toyota/Lexus, no? Here's what I'd put under each brand. And I'd have them all made in North America, even those based on Opel designs, to save money. Building a mass-market car in Europe and then importing it has become economic suicide with the strong Euro.
CHEVROLET:
CARS:
* Yet-to-be-named subcompact, based on the Opel Corsa.
* New-generation Cobalt. Basically an Astra built in the USA, available with three, four, or five doors. Include a Cobalt SS with the 260hp turbo four, of course.
* Malibu. Unchanged.
* Lucerne. Unchanged from the Buick. Large, soft, FWD sedans still sell quite well where I live.
* Impala. Pontiac G8, rebadged as a Chevy.
* Camaro.
* Corvette.
* Solstice. I'm not even sure they should keep the current model. Sales tanked after the first year, and it's got some serious flaws in the design (no cargo with the roof down, for example). Maybe keep the idea of an entry-level roadster, but go back to the drawing board. Use a slightly-shrunken C6 Corvette platform when the C7 Corvette comes out, with more mainstream materials than a C6 Corvette to keep costs down, and a turbo four engine? Available in coupe and convertible form.
TRUCKS:
* Silverado. Essentially unchanged.
* A yet-to-be-named unibody pickup based on the Lambda platform. As much as people bash the Ridgeline online, they sell like wildfire even in import-hostile Medford, and they make a ton of sense for "personal-use" pickups (hauling motorcycles, ATVs, and materials for do-it-yourself home-fix-it projects).
* Kill the Colorado and give up on the compact body-on-frame pickup market. I think it's been a sales disaster (but I don't have hard numbers), and I think a stripped Silverado work truck and a Lambda unibody pickup would absorb most people who did buy Colorados.
SUVs/CUVs:
* New-generation HHR. Take an Opel Zafira compact MPV and give it retro American lines. Optional AWD. This will replace both the HHR and mainstream compact CUVs like the Vue and Equinox.
* Traverse. The current Lambda CUV.
* Suburban. I suspect these will keep selling, though in smaller numbers.
CADILLAC:
* ATS: Compact four-door coupe with the 260hp turbo four or a 400ish-hp small block. Gateway drug to Cadillac.
* CTS: Unchanged. The second-generation is pretty stellar as is.
* STS: New generation, built with the love that the CTS got. Available in short and long wheelbase (like they do in China). The LWB version will eclipse the DTS.
* Yet-to-be-named compact crossover. Looks like the Provoq concept, uses the platform of the new Vue.
* Yet-to-be-named large crossover. Lambda platform. It would meet the market demand currently filled by the Enclave.
* XLR: New generation, built with the love that the CTS got.
* Escalade: Because Fitty doesn't care about gas prices.