Currently, ForeignStructuredUpload has a hardcoded template, which is used to provide more information for a file (I assume it's taken from commonswiki):
https://github.com/wikimedia/mediawiki/blob/74fa14ac787da8eccae118920e3f74732f3e1b4c/resources/src/mediawiki/mediawiki.ForeignStructuredUpload.js#L85-L104

That works great, if the target for an upload is commonswiki, or a wiki, where the template is created/present. But, if I think about many third party wikis, which probably use another language (like german), and already has a localized template, it sounds difficult to advise them to maintain two tmeplates, the localized one, which they're using for ages, and a english one, which can be taken from commonswiki, but maybe needs some adjustments.

It would be great, if the module would try to get a template from an own message key (which could be created on-wiki) and replaces some "magic words" with the information it already give. If the message key isn't present, it would fall back to the current form.