Hi!
Yes, you can do what is proposed but you’ll need a Managed Switch with VLAN support.
Else it won’t work.
We’ve done this on several smaller routers such as Transit & BR1 Mini with only 1 LAN & WAN port, but multiple VLAN WAN.
We used here the LAN port as a trunk port ot the switch with pre-configured WAN VLANs.
