Hello,
It would require a custom development but that's something possible.
Currently, there is a "vendor location filter" which allow to filter the vendor based on the "locations" they handle (can be postcodes or cities). The feature is provided by two plugins and a module, one to filter the HikaShop products, one to filter the HikaMarket vendors and the module to perform the selection of the postcode or city.
You can use the code of these plugins to create your owns and create another kind of filter which would feet to your specifications.
In the mean time, I will add your suggestion in our TODO list.
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.