Thank you for sharing your elegant system. Studying it, I like it.
I have an absolute failsafe method to insure that my green knob is reinstalled before I pull. Its called a "power tongue jack" Power is cut to everything including the power tongue jack. I can't hitch without power to my tongue jack.
Yes, It is prudent to insure that the power is connected to the braking system. A reminder on the tongue jack, dashboard, tag on the 7-pin connector etc. is necessary if one has a manual jack.
A dead battery is illegal no matter what. It is prudent for the owner to make sure it is charged and ready to act.
I agree, that there must be something in place to insure that the battery is live and powering the emergency braking system before pulling. However, this is a requirement with or without a battery disconnect.
Thanks for sharing the alternative method
Jeremiah