Horizontal mirroring would be an incredible time saver.
Edit: There is definitely something very wrong with the ghosting mechanics.
3k bricks, 1 brick to ghost: dupe the build, ghosting takes around 3 minutes during which I get around 1 frame every 10 seconds.
Planting: Around 5 minutes of insanely low framerate, wait it out, 10 minutes later still lagging to death but visually it seems all bricks are there. Keep pressing the numpad 0 hoping one signal will get through. As soon as it does I get +200 FPS and all bricks are there. Player is permanently stuck in the brick planting animations (looks like a seizure, it plays the animation every ~20ms), Self Delete does not cancel the animation. Disconnecting and reconnecting works. I'm on my own internet server.
Sometimes I can dupe the build just fine in just ~1 minute, but the planting just kills of FPS. Sometimes the planting is fine and duping destroys my framerate.
Edit2: trace(1), causes an infinite loop even with default add-ons. Even though the old duplicator had errors, messier code, and not as fancy features, it worked 100% and was fast. I've yet to successfully dupe more than 1k bricks with Duplorcator.