@pento What real-world problem is this supposed to solve? As Moin mentioned, empty strings do not show up on Crowdin, so they can’t be translated. Also, in my experience, translators do not have enough knowledge to come up with keywords that do not exist in the English source file.
If we want translators to add new keywords, then we need clear instructions on each string how and why they need to come up with new keywords, and the strings must not be empty. IMO we shouldn’t put this task on the shoulders of translators.