Simplify listing items with customizable forms for marketplace admins
The WooCommerce backend is pretty overwhelming and complicated, especially the product area. Listing an item should be made easier for vendors, and possibly guided, like a walkthrough. When you're running a multi-vendor marketplace, the backend needs to be easily comprehensible, otherwise your users won't list items. Ignite's Vendor Stores offers the option to cut down the number of fields visible in the backend, but it's still too complicated and vendors might miss or fail to fill in some of the fields.
Please have a look at Easy Digital Downloads + Frontend Submissions. With FES you can easily setup forms and add all the fields you find necessary. You can do the same for user profiles. Give the admin the option to label attributes that vendors will later find as predefined options to select from (dropdown list, radio buttons, check boxes, dropdown list with check boxes), such as size and color, when listing an item for sale. The former "add product" area should no longer be visible when using the forms or at least look much simpler. You could also add the possibility to not allow users to see the backend at all, so that these forms integrate with the design of the theme (the Marketify theme offers this option). These features would be especially beneficial for marketplaces with physical products as there are currently no satisfying solutions available (for digital products it's much easier, s.a.).