Kev has it exactly right. As I said up above, "If it's in the same VM, use internal://. If it's on another server, use http:// or https://. If you don't want to be dependent on the availability of the other server, use file:// or classpath://. What's the problem here?"
The problem is that you introduce a special protocol for the same server, which is overkill. This complicates things for people, who will likely not know about this "special feature". They will also have to be aware of this when services get moved between environments, and update it accordingly. All of this knowledge overhead to avoid a server freeze.