Networking issue: two routers with the same IP

[Frank Denis]

 Hello,
 
 I currently have a remote server with a trivial network setup:
 
[Server 10.0.0.1]-----[NAT router 10.0.0.30 - external IP 1]-----ADSL

 A second ADSL line and router have just been added. Unfortunately I have no
control over the routers. Both routers come with the same IP address, it's
why I have to setup something like this:
 
       10.0.0.1|-----[NAT router 10.0.0.30 - external IP 1]-----ADSL 1
[Server         |
       10.0.0.2|-----[NAT router 10.0.0.30 - external IP 2]-----ADSL 2
        
 Eacher router has a dedicated network interface on the server. I don't need
bandwidth aggregation nor load balancing, but the server should be able to
receive packets from external IP 1 and external IP 2.

 Is such a setup possible with OpenBSD? How would you do it?
 
 Thanks in advance for your help,
 
          -Frank.