Best solution for multi-route failover to remote site
I have a customer that has 2 M370's about 4 miles apart. They have always been connected via 1 P2P wireless antenna and routing traffic between the 2 firewalls. Recently I setup VPN failover using OSPF as explained here https://www.watchguard.com/help/docs/help-center/en-US/Content/en-US/Fireware/configuration_examples/vpn_failover_config_example.html
Now to complicate it even more here is what I now need to do. Customer upgraded the P2P link to AirFiber and wants to keep the old P2P as a failover. So the failover path is as follows. AirFiber, Old P2P, then BOVPN. Another factor to this is potentially dedicating the old P2P link for replication backup traffic.
My question is what approach should I take for this? Could I use the SD-WAN routing feature and use a BOVPN virtual interface to route and failover as needed? Or should I stick with dynamic routing? Any ideas?