Hi Andreas,
Nice additions! This year I’ve also been working on adding support for large fonts:
If you have your code up on GitHub, you can send a link to it, so I can see your changes and see if it’s something I want to include in SmartMatrix Library. The new Adafruit_GFX layers already include a scaling option for their basic font, and large font options that don’t require scaling, so I’m not sure that a new scaling feature for the old graphics code will be that useful after SmartMatrix Library 4.0 is released. Thank you for sharing though!