You would have to use a third device with an out of band management connection to make this possible.
For example, you could use a raspberry pi at the remote site with a console connection to the router. Have the raspberry pi scp the config from the "hot" router, and then copy that via the serial console port to the backup router.
I searched for documentation on how to use SCP over serial as I've only used it over a network connection. So far I only found the following...
Console allows you to use XMODEM. It is very slow, and IOS would take about an hour to load, but it is still very usable, and speed would not matter in your case. Get configuration from production router, wither over TFTP or otherwise. Also you can connect to it through console, and do a copy "startup-config xmodem:" (Don't forget to start XMODEM in your console, by selecting XMODEM RECEIVE option) Then connect to backup router with console, and do a "copy xmodem: startup-config".
Do you have or know of a link that I can follow on how to do this on a Raspberry Pi device and Cisco router? Also, do you know of a Raspberry pi device or similar that runs on DC? I'm not familiar with the latest Android devices, what cable would you use to connect the Raspberry pi device? Is it the USB cable that comes with it and then connect it to a female to female USB converter cable to a USB to serial converter cable to a console cable to the Cisco router's console port?
Is there or is there a way to have another connection on the Raspberry Pi device to connect it to the backup router?
Another potential option. Configure the standby router with its own dedicated IP address. Copy the live routers config to the backup router but call the config something like backup-config, instead of startup-config. Then when you cutover, you could rename the files and reboot. They want it to be an automated process. When and if the primary router fails, the person onsite that would do the swap wouldn't have access to login to the routers.
Another option, put a pair of USB sticks in the backup router. The primary USB stick (which you boot from) has a startup-config that gives it a unique IP. Then copy the live routers config to the secondary USB stick.
Then to make the environment live, swap the USB sticks over. I need to search for booting from & copying to a USB stick on the routers. I'm assuming that I would still use SCP to copy from the primary router through the console serial port to a Raspberry Pi device then through the backup router's console serial port to the secondary USB stick.
