One way to "lighten up" a bag is to find a way to make it ventilate more.

I have used boots to prop up the sides of a bag to get more airflow around the body, and there are bound to be other tricks to try based on somehow raising up parts of the bag.

It is amazing how cooling it can be if you only cover the top of your body (Torso) and leave your legs in the breeze.

There is no law that demands you sleep with the bag completely covering you..... and there is no law that requires only ham and eggs or bacon sausage or pancakes for breakfast. Many people live as if such laws existed.