I stumbeled across this requirement yet again today.
It seems an evergreen going back to an issue in Tracker by Martin Dougiamas from 2012.
Maybe nowadays this is feasible? It is a great gain of course that Tim Hunt will be present in Zürich.
En réponse à Luca Bösch
Re: Rubrics (advanced grading) for quiz essay questions
par Katarzyna Potocka,
Hey Luca, you are a MoodleMoot DACH DevCamp Pro (MMDDCP???) - so you know what you have to do … prepare the idea, pitch at the DevCamp, and convince 2-3 people to work with you or by themselves on the idea during the DevCamp… 
I have worked on quite a few assignment advanced grading methods e.g. https://github.com/marcusgreen/moodle-gradingform_btec
And from that I would say don't be strongly influenced by how that was done.