This is a functionality/feature that I needed for my multi-vendor platform. Let me explain in detail.
My platform sells premium products that is available for registered users of the platform only. Products are not visible to guest users or the world. Now some of my vendors require that their products should be visible to a subset of the registered customers and they should have the control to which customers it is visible.
To achieve the feature, I require a request-approval functionality using which the customers can send a request to vendor to view its products(like a customer can send a user group request to admin) and vendor can approve or reject the request, after reviewing the details of the customer.
To achieve the above, currently I think we can use user-groups, but creation of a user group and approval of user group requests lies with the platform admin(Unless I've missed some features of Cs-cart Multi-vendor).
Instead I require that, Vendors should be able to create at-least one user-group 'UG' and vendor administrator should have the control to approve or reject the requests for 'UG'. This user-group 'UG' will not be available/visible to other vendors. This is automate the whole process and avoid a lot of confusion and burden on the platform admin.
Views and suggestions please.