I was having the same problem and I think I've finally found the solution, although it is still quite limiting:
You can do that here. I'm currently doing this in my shop.
We can be "SOLD OUT" in the Philippine market, but can still sell when someone accesses it outside the Philippines, for example the US, since we have stocks in the PH and the US.
The only concern here is that your variants are severely limited - a max of two for the product and the third would be accessed by the app. Any more and the app won't work. Plus it can only work on certain themes and doesn't work well with other apps that has to do with changing the prices on the actual live product page.
Hope this helped!
P.S. It might not work correctly right away but you can simply message the app developer for them to fix the problem if there was any.
I just looked at it, but I think it's not even 50% of the solution that most of the Shopify store owners are discussing here.
We are looking to be able:
Also, we want to keep everything as native to Shopify as possible, so we don't run into compatibility issues down the line.
Fortunately, our app provides with this functionality