I may have finally found my limit of using ffmpeg as my all purpose video editor; dynamic effects aren't really possible. It looks like they might be, but also not really, and if I want my video to have an increasing fisheye lens until it becomes a kaleidoscope-esque blur of colors, I don't think ffmpeg can do it for once.
It took me a while but I'm still sad that I've found something that I actually can't do. Not reasonably, anyway.