Hi Swenja,
Than you for your idea to help us improve SDL TMS. In this case, the functionality that you're suggesting is not in our current plans and future innovations in quality assessment will be implemented in SDL Language Cloud. If you require this functionality in SDL TMS then, for now, you'll need to engage with Professional Services who will be able to provide a quotation for adding this functionality.
Contrary to what you have learned, SDL Language Cloud will have a feature-rich quality rating model and will provide comprehensive reporting and decision making based on feedback received for translations.
Regards,
David