Same requirement in our biz. We're coming off Weebly and shopping eCommerce platform vendors, developer wants us to go SquareSpace, but only WooCommerce seems to have the per item shipping. This will cost us more on web production, but we'll not lose on shipping $. SQSP would be a slam dunk if this was enabled.
I echo another comment in different same topic thread: "Hurry up SQSP and get this feature implemented. I am losing money on shipping and actively searching for an alternative platform. " +1