Hello !
Is it possible that a vendor can setup within the HikaShop Multi Vendor/Auction to allow only users they choose to bid on their listings?
Is it possible they can grant and remove that access to bid on their listings without Admin interference?
Sure, you'll just have to create your Auction as if you were creating it through your Hikashop back-end, set the "Auction" option to YES and use the "Access level" option to restrict the access to your auction to a specified Joomla group.
Best regards,
Mohamed Thelji.