The problem is that the packing list can be only be pulled from "sales order" templates.
Our biggest issue is items that have been invoiced already (and are marked as closed on the order) still show up on packing slips. We aren't sending these again, so why should they show up? We want open items to show up on the packing slip but we do not want the closed items. Packing slips can only be customized from "sales order" templates and those pull all items.