The main reason you've likely never seen it done that way is because it's not a survival-applicable method, since command blocks are creative-only. I guess the benefit of this method, though, is that its range is practically unlimited.
I actually see a cleaner way to do this within render distance, but I'm not sure it's possible yet.
Instead of teleporting the player, you could have a stored entity used for the teleportation. Instead of naming the player in the @ command, you use the stored entity. This could be anything from a drone player to a specific NPC (if that is possible). Just have a 2x1 storage cell to hold it. All return commands would simply send the mob back to its storage cell, while the player is left unaffected.
Hmm, nice idea, kind of like regular hex's old nether messaging network.
I have a way to remove the player necessity, but it's really derpy. Essentially you make a custom spawner for zombies with a big player detection radius (enough to include anyone using the machine). put it in a dark area next to a redstone lamp. If you pulse the lamp off, a zombie will spawn at the location and velocity that you choose, allowing you to fire a high-speed zombie in exactlly the right direction to land on a pressure plate, transmitting the signal.
Ive never experimented with custom mob spawners
is it a world edit function? or mc edit?