Hi Tim,
Yes I did build and test it out. The main 'issue' I have is that the connectivity and vpn out the device 'pf_internet' from 'pf_internal' is used for other services too.
If, on the device 'pf_internal' 192.168.166.x interface, I set a gateway of pf_internet (192.168.166.x) but with a monitor of an IP across the tunnel, I believe yes, this would work. However, if only the tunnel to that remote IP being monitored goes down, I run the risk of causing failover for other services, even when the rest of the connections are up.
– I hope you understand what I mean?
My workaround for the moment is to have static routes, specific for the remote IP, disabled on pf_internal. In the case of failure of ther tunnel, the static routes are simply enabled.
--- Yes, I know.... Manual intervention like this is not ideal, I'm just not seeing any other way around this scenario.