Nginx proxy with multiple ips behind VPN

Hi
I have a tornadoweb server hosted on a machine and nginx server on top on that machine. All routes to nginx are then redirected to the tornadoweb server.

The tornadoweb server requests information from some other systems that are behind vpns. nginx is able to proxy pass those because openvpn is also installed on the same system.

Now the problem is we will be adding 100 more ips that are behind vpns. How is it best solvable. Right now I can only think of adding 100 locations in the sites-available default configuration, but when it will increase to 1000 then ill have to add 1000 configs in that file.

Is there a better dynamic solution for this instead of adding an entry for each system behind vpn.

I tried hosting another server on the same machine that would access the VPNS only. lets say tornado2. Instead of adding those 100 lines i just added the url path of the tornado2 but that didnt work it gives me error that the server took too long to talk to the vpn ip. But the proxy config for the 100 ips works just fine.