I loved the OP's Fusion 360 design and made some modifications. The hinge design is ingenious and fully parametric, but the design would break under certain circumstances. I made the following changes:

1. Magnets can be sized up to 10mm
2. Added a small slot to remove the magnets
3. Fixed the design instability for width and magnet diameter
4. Added a new parameter called lidHeight to make the lid smaller relative to the box height. (Smaller lid version needs supports)
5. Ability to generate both small and full lid versions simply by moving the history marker.

I included the Fusion360 design file and 100x75mm .st's with 12mm lid and full height lid