This is something we have considered, but not all services offer a language option, and those that do support multiple languages don't necessarily list all the languages they officially support!

If it was available, it would use that language for supported services, and then default to English if no language options are available.

Definitely on the roadmap for us to handle better.

You may also give the option “additional instructions” for the default option. Then the user can add “output in...”.

Yes, however then it will have conflicting directives as the original role prompts include that it should be in English...