Hello! Severe, progressive visual impairment (and eventually legal blindness) run in my family. Due to my sister's performance problems with common Windows magnification software and my own positive experiences with macOS' built-in fullscreen magnifier, I recently bought my sister a Mac in the hopes that she might enjoy a more reliable, usable computing experience. (For us, BTT's killer feature is (oddly enough) the pointer size toggle action, which she's used to relying on with ZoomText on Windows, but is missing on macOS.)
One of our frustrations with macOS is that the increment by which fullscreen zoom is adjusted via the keyboard is way too small and not configurable. I've noticed that BTT can do configurable-increment 'smooth' zooming, presumably by emulating a pinch zoom gesture performed on a trackpad. For low vision users like me and my sister, the ability to configure macOS' other zoom gesture (three-finger tap-tap-swipe up/down) as an action much the same way would be a huge boon. The ability to zoom in by larger/configurable increments with a keybind is a basic feature common to nearly all fullscreen magnification software, and BTT could help restore this missing feature to macOS in its way. That would be awesome! 
(Apologies if there's an existing way to accomplish this with BTT and I've missed it.)
PS: Andreas, hackability and accessibility are deeply intertwined. By making macOS input devices easier to customize, emulate, and automate, you've already helped make macOS more accessible. Thanks for that. 