However, I think this is good for some instances where .. well here's a test case from our site.

I need States for domestic orders, of course. If someone from Albany, NY orders a product, we need to know that it's not meant to go to Albany, GA.

Unfortunately there are many countries that don't have "Zones" per se, Finland being one of them. Which means we cannot require the Zone field be entered for an order to complete.

The result of this setup means that we've had some domestic orders come through, and the user has not specified a state. For most cases this works (since the majority of our content is downloadable) but I think giving an option to force a state requirement in a domestic order is the way to go. Perhaps a variable in UC such as "Force Zone field requirement in domestic orders" or something to that effect.

If this is something trivial, perhaps I could write a contrib, but it's something to consider IMO.