Multiple WAN ips with corresponding local gateways

I have a range of static IPs I got from my ISP. What I want to do is to do as I do with the primary IP.
Set it up with a corresponding gateway like 192.168.1.1 and computers in the LAN can specify this, and use NAT to open ports etc.

So in example I have the public IP from ISP which is 1.2.3.194-1.2.3.197. 193 is the ISP gateway and 198 is the broadcast.

So I set up the router as normal with WAN, 1.2.3.194, and local IP 192.168.1.1.
Then I want 1.2.3.195 -> 192.168.1.2. Then a computer's...

Multiple WAN ips with corresponding local gateways