Can you use XMLRPC sync but not CARP/HA pfsync / state synchronization to create a "manual failover" type cluster?

[bp81]

As the title asks. I have some locations with single DHCP issued WAN IP addresses and so aren't suitable for a traditional CARP/HA setup, but I'd still like to have some hardware redundancy.

Would it possible to run two identical pfsense routers an implement XMLRPC sync through a dedicated interface, but not configure CARP? I envision having my primary router having its normal connections to the ISP demarc on the WAN side and to the internal network switch on LAN side, and then the point to point XMLRPC sync connection to the secondary router. The secondary router would have an identical configuration, but the only physical connection it would have would be the XMLRPC sync interface back to the primary router.

In the case of a failure of the primary router, on site staff would be instructed to move all cables (except the XMLRPC sync cable) from the failed primary router to the same port on the secondary router.

Downsides: no automatic failover, and states are not maintained through failover. Upsides is that I don't have an internet outage at a location for hours or days as I wait for IT staff to arrive or replacement router to arrive.

Would this work?