This is great! I'd love to see more wrappers like these for ffmpeg. Despite 5 years of using it, I can rarely run any ffmpeg commands without looking at StackOverflow. I wrote a similarly-inspired wrapper because of this as well, with a different subset of features, some of which rely on moviepy: https://github.com/achalddave/vid
Would be great if vdx learned more "common" ffmpeg features (creating a slideshow from a set of images, speeding up videos, simple drawing, etc.) while maintaining its simplicity!