I've often thought it would be interesting to see an ebook format that would allow one to toggle between versions of the text or display text inline as some kin

I've often thought it would be interesting to see an ebook format that would allow one to toggle between versions of the text or display text inline as some kind of diff. I say this because there are some authors that I read who have revised their works many times, and sometimes I prefer an earlier version over a later revision.