As we all know the DDNS page existed for many years, way before MultiWAN was even discussed...
Overall the current DDNS page does the job greately for single WAN, but say you want to be able to reach externally each WAN you have in a multiWAN scenario (for whatever reason like VPN-in traffic sharing, etc). We're currently unable to bind each WAN to a separate DDNS service as the IP address is unique for the page/config.
There might be a little redesign...
MultiWAN - DDNS - single IP interface limitation
Overall the current DDNS page does the job greately for single WAN, but say you want to be able to reach externally each WAN you have in a multiWAN scenario (for whatever reason like VPN-in traffic sharing, etc). We're currently unable to bind each WAN to a separate DDNS service as the IP address is unique for the page/config.

There might be a little redesign...
MultiWAN - DDNS - single IP interface limitation