Actually, a second network interface with another public IP is sufficient if the (virtual) hardware meets all the requirements (CPU/RAM/DISK). You can either run them side by side, within a container solution, or otherwise isolated.
If you still want to run in only one server, then Google for linux network namespaces.
You can run various process each in separate context.
But you will still need various public IP address. You can then use NAT or IP tunnels to communicate to internet.
It's a bit complex, but it works.
You could run on the same physical hardware (with different IPs), but imo you should consider two completely separate solutions. Possible weak points include hardware failure and ISP issues, both of which would stop payments from both nodes. Is it really worth scrimping over? Different locations / countries might also protect you (and the network) from legal attacks.