DB Driven custom field?

-- HikaShop version -- : 3.3
-- Joomla version -- : 3.8.5
-- PHP version -- : 7.1.14

I don't think this is currently included, but I'm thinking about updating a customer's very old, custom online order system using Hikashop as it's skeleton. The old system's product definitions included several fields that were populated by lookup values from large, simple indexes (stored in database tables of their own).

Hikashop's simple dropdown field types require us to enter each value, which is perfectly understandable. However, if Hikashop has incorporated Joomla form fields, there is one which looks up a pair of values from a database.

Is there any way to create a new "field type" for use in Hikashop's custom fields interface which uses JFormFieldSQL? If not, maybe it could use a lookup list from a document written in XML or preferably JSON?

I fear I'm looking at the beginning of a really massive headache, here.

Cool! Thank you for the lead.

If I can make it work gracefully, I'll post it back to you here.