Ok... but almost all that you said is a UX Issue...
Imagine an UI with a circle and the spritz box above. You put your thumb in the middle, push right it starts to show the words forward, push farther from midle => faster. Push it left => slower. Left after middle, rewinding text.
You could even use up, down to go back entiry frases or paragraphs.
Regarding linearity, you could use color/color fading to wrap phrases, or show two to four words per time moving just the red letter according to speed.
Why wouldn't they just implement a stop/start button and a zoom out/in button? If you want to return to a missed word or reread a section, zoom out to see a page and then touch a word.
Imagine an UI with a circle and the spritz box above. You put your thumb in the middle, push right it starts to show the words forward, push farther from midle => faster. Push it left => slower. Left after middle, rewinding text.
You could even use up, down to go back entiry frases or paragraphs.
Regarding linearity, you could use color/color fading to wrap phrases, or show two to four words per time moving just the red letter according to speed.
Personally... I think it's an amazing Idea! :)