Adding Product Difficulty Level For Picking/Packing Purposes - Picker/Packer Productivity

Just switched to PDA scanners and noticed we can track picking and packing productivity which is great. The only issue we have is that we have a varying level of difficulty in picking/packing orders (mostly packing) as some products may require additional packaging measures vs others that simply slide into a mailing or bubble bag. It would be great to have a scale of say 1-3 (Easy / Medium / Difficult) that could be set when creating the product that could add to a users statistics. That way we can assess fairness when comparing statistics and ensure an even spread of trickier products.