1. CADILLAC: This is probably the easiest one of all.
Step 0. Change the FONT of how you write Cadillac to something contemporary and create a clear Vision for the brand - "American Luxury" does not mean a thing.
Step 1. Do not change names of cars. Stick with what exists today i.e. CTS, STS, SRX and Escalade.
Step 2. Dump DTS. Nothing that is not a rear-wheel or all-wheel drive for this lineup.
Step 3. Introduce a smaller cross over based on Chevy Equinox Platform.
Step 4. Fix XLR - it can't be a Corvette with a sheetmetal drawn with just a ruler. High tech suspension and engines are a must in this category. Oxcart leafspring suspension and pushrod V8's just don't cut it irrespective of their credentials. Look to Audi for Interior inspiration.
Step 5. Dump all the current hybrids in the lineup. Don't waste time creating pointless Hybrids out of Escalades.
Step 6. Take time to develop an exclusive Hybrid car. Make it look geeky like the prius or insight to get proper street cred. This segment is waiting for a properly styled premium hybrid.
Step 7. Do not use engines that are not Direct Injections or transmissions that have anything less than 6 speeds.
Step 8. Train the dealers. Send them to the Lexus or Infiniti school, NOT BMW.
Why not do any or all of the above? Seems like simple commom sense to me.
Buick is next ...