These are all great options to try to curtail attempts to trick crafters into using their materials.
Might I also suggest adding a warning message to crafters who take on work orders that states something along the lines of “You are about to use some of your own materials to complete this work order. Continue?” This will alert a crafter to carefully look over a work order before they proceed.
Just wanted to Edit my post: Apparently the suggestion I made has already been added in a more recent update!