As I said the design does not count: lots were made by Italian design companies.
It is the conception of the whole car which counts.

For me it is the original of the base model which counts, but others wanted to use the country of the "modified" model for sedan versions etc. It is true that in that case it is not only the design but other technical aspects of the car which had to be changed/studied.
But this could be solved when it will be possible to specify two origins: for the Astra Sedan it would be DE+BR for example.