This is a user-to-user technical support forum. We just have the collected wisdom of having read lots of posts, from people trying to do the same thing and finding they cannot do it.
Keep in mind that some countries have restrictions on features allowed, so the Apple Watches sold in those countries have different software. So on a country by country basis Apple sells its Apple Watches with country specific software on each.
Selling the wrong country's Apple Watch to someone in a different country, is just asking for support headaches, that will far out weight any profits they could get from selling a few cross border Apple Watches.