A customer would find it useful to configure delivery charges which are automatically calculated based on the weight of the product. They would still need the option to manually type in the delivery charge if the automatically calculated delivery needed changing.
We've added some weight calculations to the quote/order line entity. You can't do delivery charges on that information yet, but obviously this is a step towards that. Just thought I'd let you know that the line weight is now available for reporting purposes if that's useful to anyone.