WAN Failover with a Single Dynamic IP Address

A networking setup I manage at a nonprofit involves two OPNsense machines in a CARP/HA setup. Their current ISP (Comcast business) gives them a static /29 pool so I’m able to perform proper CARP on the WAN interface. Looking to move to a fiber ISP that charges extra for static IP’s. Because of this, I’m trying to find a way to perform CARP or some kind of failover on the WAN interface with a single dynamic IP. I’m aware this custom script: https://gist.github.com/spali/2da4f23e488219504b2ada12ac59a7dc but I’d prefer something officially supported so it won’t potentially break after updates. I also wrote up this GitHub feature request: https://gist.github.com/spali/2da4f23e488219504b2ada12ac59a7dc but doesn’t look like it’s gained much traction. Any advice would be appreciated.