Even if both of the failover interfaces go down it wont affect the traffic flow. Also if the switch is being monitored this will get detected and can be solved easily. If you still want redundant failover links, using seperate switches will be good idea.
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...