Ok so tried the autoconf setup and got this
Warning: priority inversion [interfaces ethernet eth0 pppoe 0 ipv6 address](400) <= [interfaces ethernet eth0 pppoe 0](400) changing [interfaces ethernet eth0 pppoe 0 ipv6 address] to (401) [ interfaces ethernet eth0 pppoe 0 ipv6 address autoconf ] Address auto-configuration will be enabled when interface comes up.
Show interfaces I get
show interfaces ethernet eth0 { description "Internet (PPPoE)" duplex auto pppoe 0 { default-route auto dhcpv6-pd { pd 0 { interface eth1 { host-address ::1 prefix-id :1 service slaac } interface eth2 { host-address ::1 prefix-id :2 service slaac } prefix-length /48 } rapid-commit enable } firewall { in { ipv6-name WANv6_IN name WAN_IN } local { ipv6-name WANv6_LOCAL name WAN_LOCAL } } ipv6 { address { autoconf } } mtu 1492 name-server auto password ********* user-id ********* } speed auto } ethernet eth1 { address 192.168.1.1/24 description Local duplex auto speed auto } ethernet eth2 { address 192.168.2.1/24 description "Local 2" duplex auto speed auto } ethernet eth3 { duplex auto speed auto } loopback lo { }