Trying to copy a unifi feature which is where you can create a VLAN and tag it to a WAN2 and assign it to a specific WAN.
Useful for IPTV, management networks for specific hardware, and more
For example if you have VLAN2 and WAN2 you can assign that via the webUI and then if you create an SSID with that VLAN tag it will route traffic out that specific WAN