that was a question?
You are right, the amount of water I carry would have a weight penalty, but the amount of fuel I wouldn't be wasting is worth it. Also, water (even distilled) is cheaper than gasoline (last time I checked)
I dont know if your turbo and fuel mileage generalization is very good either, however, I'm not going to argue with your generalization. All I can tell you is that whatever car I get, I will be able to make it more efficient by using a turbocharger, and I won't be the first to do it.