TYPO3 Updating non-default-language records with exclude fields

Question

I have my site in both English and German. For my Extbase records, I configure all the fields with:

  'l10n_mode' => 'exclude',
  'l10n_display' => 'defaultAsReadonly',

except those input and text fields which contain text that I want to translate. This works as expected at a lower (TCA) level: If I want to change any of the excluded fields I change it in the English (default) record and the change is also reflected in the German record.

But I have a big problem in the frontend, in the Controller Update actions: when I'm visiting my website in German, and I update a German record changing one of the excluded fields, this change is only done for the German record and doesn't get reflected in the English record. Moreover, if I then change anything in the record through the backend, this change I made to the German record's field gets overwritten by the English record's value and therefore lost.

Is there any way to solve this kind of situations in an idiomatic manner for TYPO3's Extbase?

Thanks a lot in advance!