Hi,
It is something we have in our TODO list but which is not implemented for the moment.
Our idea is to have "roles" rights for the vendors.
By having a valid subscription, the vendor will have a role and when the subscription will end, it will loose his role.
Roles would be like joomla groups, so a role will gives permissions and a vendor could have several roles.
After that, for the moment, the ACL on HikaMarket just allow or not to edit or access to some values. It does not create limitation like the number of products.
This feature could be currently done using a plugin. But like I said, it is something we want to implement in HikaMarket in the future (but it is a quite important development).
For product limitations, payment gateways, product categories. It is possible to create the feature using a plugin.
For the discount limitation, it will be more complex and I am not sure that it could be done like that using a plugin.
Regards,