Hi,
I think the best at this moment is to change the global ACL in HikaMarket.
www.hikashop.com/en/hikashop/143-hikamar....html#configtab_main
You can remove the right for "add" product and category ; And you can remove the "vendor" rights too.
After that, you can override the rights for a specific vendor and for a specific user.
The rights for a vendor completely override the global rights.
The rights for a user are just restrictive rights, you can give more rights on a user than on his vendor (so you can "just" remove accesses).
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.