I totally respect the notion, there are no drawbacks to trying to make a vehicle lighter(except the creature comforts you loss in the process) but you have to think of weight percentage. It is a 5,800 pound beast, you need to lose a large percentage to make a difference, say 5-10%. Even at 5% you'd need to lose 240lbs....that's a lot of stuff.
I did look into it because I found out the Tahoe Hybrid has an aluminum hood, the problem is that the whole front clip is different too.
My plan is to run without the 3rd row when not needed (those two little seats weigh about 60lbs each) and get some low resistance tires when new ones are needed. Other than that I rarely fill the tank completely and I try to keep her in 4cyl mode as much as possible. Even with all that I'm getting only 15mpg. I didn't buy her to be effiecient, I bought her to tow and hold a bunch of people and be comfortable.