Any ideas on how to autoassign the first /64 of the WAN ip to my LAN interface? Do I need to script it or can it be done through autoconfigure?
Create a pool, let’s say “ipv6_pool” containing your (first if prefix length is less than 64) /64 WAN range.
Set LAN interface address to ::1/64 from pool “ipv6_pool”.
This will assign the address ::1/64 to your interface.
And the same pool can be used to assign addresses automatically to your LAN devices via ND (just enable ND advertisement on your LAN interface).
If your IPv6 range is assigned via DHCPv6, create/populate the pool from your DHCPv6 client instead of creating it manually. This will allow full automatic configuration and update of all LAN IPv6 addresses.
thanks for the reply.
I ended up doing exactly that, and had already enabled ND.
I noticed when setting it to ::/64 it repopulates the address and the IP address has a status of G - I haven’t tried it yet but I trust that it will update on the next reboot
G is ok 
and it will be repopulated on restart.
The only thing to do should be to reduce the RA lifetime in the ND configuration if you have a dynamic assigned IP, so that your LAN devices update more often.
Windows clients (didn’t studied the rest) will have a big lag on the update…
For static assignments, you can leave it at 3 days or something. Then it will practically update on connect/reconnect, which should be enough.