Watchguard allows you to do multiple gateways per tunnel also, but from my own post asking about this it doesn’t seem possible with VyOS.
Now the solution I ended up going with while working with @Viacheslav, was to setup multiple tunnels using a single WAN interface, then use the same tunnel endpoints but different metrics. Then if tunnel1 via WAN1 goes down and remote resource using metric 1 is unavailable, tunnel2 via WAN2 should be able to get to the remote resource using metric 2. That may not have been fully fleshed out in my linked post, but I am running that configuration now and just need to tie up some additional testing.