Have you ever unloaded?
One of the most important things an unloader does is make sure damaged packages are not put into the system. Wait until you witness what a few open boxes can do to these automated hubs...Not pretty.
There is no way one of these unloaders could come close to turning a door as fast as I used to when I unloaded. A machine dealing with open/damaged packages, hazmat packages, pallets, shrink wrap and gaylord boxes will be a massive waste of $$.
On top of that you will still need someone to operate/babysit these machines and sweep finished trailers. So in reality you might cut 1/2 of your unloaders but have to add back in extra $$ for added maintenance personnel and parts.
Anyone signing off on this should be fired. There are a lot of cheaper issues UPS could address with a much higher ROI.