Yes it is indeed possible to load a font from a .otf file at runtime (in fact, I implemented such a feature months ago using the ctypes module), but that's never as good as a proper first-party implementation.

@JonB , hmmm. Yeah it was getting a little tricky. Chicken before the egg thing. But I will look again. It's probably time I shut up and actually try to write something that works and does something 😱
But thanks again for your long lasting patience 👍