You scenario affects all fuel supplies. So you only can use what you have on hand.I see to convenience of the whole house natural gas unit. But the NG supply as to be intact for it to work. It takes electricity to move the NG to you know. It is not a stable if the grid goes down for any serious reasons. When the grid fell out on the east coast some years back and cascaded through several states they had NADA. Nothing. No water/NG/power. Nada.
The local water Co. Has diesel pumps but they drop out when the tanks run dry and even then they are limited as to supply volume. Same with you NG supply. It take power to run the supply loop.
Just something to consider.