Email body text in different languages based on language code
For reports it is possible to provide translation for Captions in different languages and based on Language Code for the document, system will print captions in that language.
Only thing that the additional translations have to be added to the report - and this can be done via extension. Ask Your partner to provide the English captions used in report, and You can provide the translations in all other languages that You need.
Different document layouts specifically for Customer also is an option, but I don't know any way to automatically assign a specific report ID or layout for customers. But this could be possible to add as modification when Customer card fields are modified (either Country/Region, or Currency code or the Language code)