Thanks Sebastian, great to hear you find the suggestion interesting!
Yup, Google has a variety of variable font which would profit from this integration as well. Having sliders could make font tweaking quite a playful – and unique in the WP-eco-system – experience. Just have a look at the fun website of this font foundy.
For the time being, we will look into using the code editor for modifications, as you suggested. I’ll be back if I have more questions.