Fixed Wireless WAN IP

If i could set a WAN ip to the module then i could route a subnet of ips over without needing an additional router. Right now i have a network with a cisco on the head router doing NAT. if a customer needs a public ip , i stick a router behind the canopy and set the WAN ip to the same subnet as the bridged ip of the canopy and route over the ips and put it on the LAN side and then can have public ips.

I understand how the private side of the WAN works so you always access it by luid, but if i could add a secondary ip, it would save me a piece of equipment at each install and make it a lot easier to accomplish.