any advantage to separating WAN into vlans before going to routers?

What is recommended way to deal with multiple WAN addresses (only 5) that ISP provides through one connection? I have in the past put the cable from ISP into small switch, then fed individual networks, or devices that use a WAN, from the separate ports on  the switch. I have seen networks, where everything is plugged into a large switch, and WAN IPs are available anywhere on the network you plug in, if you know the addresses. My main question is, if I am using the small switch to distribute the WAN to individual routers / devices, is there any advantage to set up Vlans, on the small switch so that port from isp is vlan'ed  (probably not a word) to each of the other ports individually, to separate WAN traffic from each other?