The main point, I believe in using Revvy internals or another agitated hopper is they are cheap. These shells won't bring in a huge income but will bring in some. Its cheaper for a player with a budget to buy a busted revvy, buy these shells and go to town.
VL did something similar years ago with the revvy. Had 140 shell, 200 and one that was like 300. Those are hard to come by nowadays.
Rotors are great loaders. They're many great loaders, but cost is key. We're talking about a guy with a 3D printer filling in orders from his basement/shop.