Instead of Nat’ing everything to the router IP you may want to NAT to many IP Addresses.
A couple of tips. In the network config add IP addresses on the WAN interface Configure ‘redirect’ sections in the Firewall config file Specify gateway and DNS on the WAN interface and enable masquerading on the LAN zone.
Links forum.openwrt.org/t/nat-1-1-implementation/159978 forum.openwrt.org/t/1-1-nat-mapping/84422/9 openwrt.org/docs/guide-user/network/wan/multiple_public_ips#configuration_examples
A couple of tips. In the network config add IP addresses on the WAN interface Configure ‘redirect’ sections in the Firewall config file Specify gateway and DNS on the WAN interface and enable masquerading on the LAN zone.
Links forum.openwrt.org/t/nat-1-1-implementation/159978 forum.openwrt.org/t/1-1-nat-mapping/84422/9 openwrt.org/docs/guide-user/network/wan/multiple_public_ips#configuration_examples