A DHCPv6 relay agent for a router needs a bit more functionality than what is offered from the current ISC dhcrelay.
The first is DHCPv6-PD awareness and the ability to execute a hook script with details of the delegated prefix so that action can be taken to add static routes for the assigned prefix.
The second is support for RFC 6939 which is insertion of the client link-layer address so that DHCPv6 servers can reference DHCPv6 hosts by MAC address rather than DUID.
I'm not currently aware of such a project.