There is an often-forgot other situation where your body needs some stored energy: sickness and accidents.
Usually people state that the salt keeps the water in the body, so if you want to lose weight you need to lower your salt intake.
But what you say kinda makes sense, I'm interested in hearing more of your ideas.
You could maybe do what you suggest by just slowly sipping a glucose solution over the course of a few hours but it would be very inefficient.