Change WAN IP with SSH/Script (3rd WAN)

Is it possible to change the WAN IP and gateway through ssh?

I have a location that needs 3 WANs:

1. Fiber for business
2. Coax for IP TV and Client Internet
3. Starlink for backup

My idea was is to either run a cron on Firewalla or another server to check for internet. If it fails, change the IP and gateway of WAN 2 so it can connect to Starlink. This might seem overkill, there are frequent area wide power and service outages.