Hi,
Ok, I see. But can't you configure JMS multisites to handle that ? (I'm not familiar with the integration as it was done by JMS themselves)
From what I know, JMS uses MySQL views for the slave websites, so it wouldn't be too far fetched to be able to have different custom product fields for example for the different description/meta data of the product for the different websites and map that to the description/meta data fields in the slave websites.
Maybe you want to contact the JMS support and see if they have some idea on how to do that ?
Actually, if you know a bit your way around in PHPMyAdmin and MySQL, you could do that with different websites on the same database with views on the hikashop_product table to map the one from the main website to the other websites with the correct columns.