Apple sauce (or any fruit puree) is a standard substitute for a fat. IME it didn’t change the texture at all. I agree with tomim tihye that its probably easiest to start out with a base recipe and then change it to fit the requirements you want.
Sugar also has long term health risks, you have to decide which can be more potentially dangerous.
tomim, do you find that baked goods come out heavier or with an aftertaste when using ww flour?