Deploy Word document generation template to new Dynamics 2016 environment.

Microsoft are treating the new document generation facility in Dynamics 2016 as the best thing since sliced bread. There are some genuine limitations with it at the moment which I've seen posted elsewhere.
But I've come across an issue with custom entities. I managed to create a template alright but then tried to install it in another environment. I wasn't trying anything fancy, just a manual install of the template. But when I added the template it bound it to the wrong entity. Now it doesn't offer me the option to choose the entity, just goes ahead and binds it to the wrong thing.
It is to due to the object type code or sometimes called the entity type code. That code is fixed for all the standard entities, but custom entities are given a number in the 10,000 range. What I've discovered is this number is not the same across environments. It's not that I've been stupid and manually created the entity, I deployed a solution as you normally do, but it issues a different type code in the new environment. You can see it easily if you can access the full url for an entity record, you know when you want to find the unique guid. The etc parameter is the entity type code.
Now this wouldn't be a problem except when you create a Word document template it adds the entity type code to the end of the namespace. you can see it when in Word and you are in the Xml mapping pane. It's there at the end of the urn. That then causes it to bind to the wrong entity when deployed into the new environment.
If you spent hours creating the template you don't want to have to repeat this in each environment.
To solve it, take the template and rename the extension from docx to zip. You will see in the extract a customxml folder and in there a file that contains the urn of the source data. You have to change the etc at the end to match the correct one in the target environment. Change any other related custom entities. Zip it back up and rename it back to docx. Load it back into the target environment and it should work. Maybe I'll find the time to write an app to do this for me because I don't see Microsoft fixing this anytime soon. Damn, sometimes Microsoft just don't think things through.