F5 HA issue as dependency is on FW

i assume you are thinking about VLAN failsafe and that doesn't care if the interfaces goes up or down, it cares about seeing traffic on that VLAN.

what you want is kinda tricky, because how would the F5 know the status of the firewall? if the traffic does indeed fall away from a VLAN that would be enough, but if anything still happens there then it isn't. isn't it possible to add a switch layer between the firewalls and F5s so it doesn't matter which F5 is active?