Everyone knows the current operations don't make sense. Having a guy load 1700-2000 pieces in 8 hours... I'm sorry 7.5 give or take after breaks etc is absolutely insane.
Hopefully, your operation has an operation report that let's you know daily the PPH for each loader. A full time operation is tough, because of the long hours, but because the packages are in the boxline for your loaders, it allows you to OJS to improve production.
You know the daily dispatch by preloader, you know the amount of volume per cage. You know how many revolutions the boxline makes in 7.5 hours. Do the math, it tells you the number of packages each preloader needs to pull from each cage each revolution. I know it's easy for me to say this, harder you to accomplish with your people, but that's what will make you successful. I would build the plan, succeed in making your PPH plan and then move on to an on car sup job. It's still a lot of hours, but it's days.