I attempted a similar effort, and found my router had critical ipv6 vulnerabilities including binding the admin and SSH to the WAN on ipv6 (not on ipv4) , and disabling IPv6 firewall altogether so the LAN services were exposed to the internet.

I had the vendor publish their GPL drop, and their upstream vendor did not even have IPv6 support in the product ( the firmware init scripts & admin UI) . So the IPv6 support in the finished product was a rushed copy-paste of IPv4 setup.

I encourage full black box testing of your IPv6 setup, as IPv6 is not in the critical path for QA or consumers, so vulns can persist for years.