While your idea of using discrete power units is interesting, we aim to fast-paced 'pedal to the metal' experience for the camping at this point.
You are also right in pointing out that switching the cams/lights on/off won't reduce your power consumption. The reason being (as for this version [1.0.0]) we are still working on the power management.
We plan to make it so the number of systems you have active will influence on how long the fuel lasts in future updates.