Including a variant segment in product type template route in Commerce 2 Is it possible to use a wildcard when specifying the template path for a Commerce 2 product type?

I want to format my URLs as /type/product/variant
Where 'variant' could be a custom field applied to the product variant.

In the settings for my product type I've tried a few things, including setting the "Category URI Format" to variations of /type/{slug}/{variant.customField} all to no avail. The template isn't found as soon as I include that third segment to the URL.

I feel this should be possible to do with Routes but having much the same problem.
Have figured out that instead of setting a template path in my product type I can leave that blank and use a custom route instead.

So in this case I set up a route for 

/type/*/* -> shop/variant

It means I need to fetch the product entry manually in the template but that's no problem and it seems to be working.