Hello,
Yes you can add Joomla accounts into the HikaMarket main vendor.
Please note that, when a user is affiliate to the main vendor he can possibility access to every orders/products/categories.
If you add users to the main vendor you have to configure their ACL to restrict them to access to elements from other vendors.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.