Interesting ideas. I like the idea of maybe making this an addon for Ren'py or one of the Unity VN plugins. That would probably be a separate project though.
As for framerate, that's also a good idea. I actually limit the eye tracking to 15FPS (and a forced update when the mouth shape changes) since it's very uncanny at higher framerates with the speed of the mouth-shapes. Letting that be a broader control would be good for anyone looking to free up some CPU or GPU on their rigs. I'll add that to my would-be-nice list for after I hit the first official release!
: ^ )
These are good ideas! Thank you for sharing.