GM needs only 3 or 4 divisions:
Chevrolet - Entry level economy, family sedans, bread and butter. Oh yeah, Corvette. And if you go with the 3 division concept, Chevy trucks.
Pontiac - Performance. Which, due to the stupidity of GM, seems to be in a quagmire as they have halted plans for the Zeta platform. How you gonna have real performance without RWD?
Cadillac - Luxury.
..... and if you go with the 4 division concept:
GMC Trucks, which would then eliminate Chevrolet trucks.
GM still has waaaaay too much redundancy and badge engineering in their corporate ladder. Trim the fat, stream line, and then 2 things will happen: they'll make more money, and then they can afford to put some of the extra profits back into making their existing cars better quality and style.
Again, there'll be a few tears shed if Buick joins Oldsmobile in the Blue Square Grave Yard, but since the last really cool car to come from Buick is the Grand National/GSX (which was last produced 18 years ago), I doubt many people will really miss it.