You could build the environment and restore the VMs. You could have a separate physical switch setup and maintain the IP addressing, but just make sure it isn't routing (or maybe not even connected) upstream. Use this setup for your VMs only.
Then you can put your management interfaces for the ESXi boxes on the real network and allow developers access via the vSphere Client. This will allow them to access the VMs with the addressing intact, but with the VMs still being completely isolated.