Hi,
Yes, it's the easiest solution that I see.
A product have a categories and all his variants have the same.
It would be possible to implement a custom plugin in order to have a filter but it would require some modifications in the HikaShop core (not a big one).
Adding some PHP code in the "product | show" view would be the faster and the easier way.
The PHP code could still connect to the database in order to make requests, load some configuration in a specific table, etc.
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.