Having come from a previous job role where I worked with Magento; I have noticed quite a few limitations to the Wix platform. One I am missing from Magneto is the addition of bundle products.
This is where a product set can control inventory across the board. So, for instance, say you want to buy a camera and a lens. These are separate products, but your not sure which lens fits the camera your after, so instead the retailer offers the ability to buy both products as a package (possibly at a discount). If the customer proceeds with this purchase, then the inventory for the corresponding separate products is updated.