Why do we need to split the template? You can just put
information before or after the template.
You can do that, or use the comment= parameter. The comment text will be placed
before the box that wraps the original description.
I don't know of translations of the original description. Do we want/need this?
For many images? If yes, another parameters, translation=, could be added, I
I suggest to discuss this at the talk page of Template:BArch-description, or, to
reach more people, the talk page of Commons:Bundesarchiv.