Remote LP Shut-Off and Battery Usage

I'm sure it would be possible to install a manual shut off valve somewhere in the system. It obviously wouldn't shut off the tank if that is inaccessible but would stop flow to the appliances. Look where the LPG piping enters the interior, it will probably be in a cabinet. Install a valve there and then remove the solenoid.

I'm confident that if I was standing there beside you I could find a way to make it work. Alas, I am not beside you, I am in front of a monitor.