Andrei, I took a look at the work order on this one:
Display SKU in generated "Order invoice" (PDF). Display it on order details page > 'products' tab and 'shipment details' page.
Is it possible to make a suggestion (or add-on)?
Can the SKU be a selectable token on the message templates?
For example %ItemVariant.SKU% as something that can be added to the store-owner only e-mail that gets sent when an order is placed. Right now, it's not on the list of available tokens.