I liked the tidy FR5 spacer demo. Then the workshop visit showed someone sorting our incoming trays by hand. That rather spoils my comparison. What would you ask them to repeat?
Repeat from the box the trays arrive in. In our toolroom a neat tray on the bench usually means somebody has already done work. Might be perfectly reasonable work, but it needs a person and a place in your plan.
Our comparison changed once the person doing replenishment attended the demo. Could your actual loader go and judge the preparation and empty-tray work?
Oscar's distinction is fair, and Louis's answer makes it extra work here. I'd still consider special trays if they remove enough trouble. But show the transfer into them, not only the nice bit afterwards.
That needs the spacer supplier's agreement. It also changes where the empty trays go. I would keep it as a separate option until somebody prices both directions.
Supplier won't change the packing for our orders. We've dropped the special-tray option after pricing the extra handling. Loader is joining a repeat of the workshop demo with our usual incoming trays; thanks Henry, she spotted the empty stack nobody had allocated space for.