Comment 13 for bug 338002

Reviews actually have a pretty nice system by which they can be superseded and have back/forward links to the other versions of that submission. (You could do more, but the basic structure is good.)

So maybe this should fit in with that somehow. Perhaps there is a user choice as to whether these are small changes and stay in the same review, or large changes that need a new review to start. In practice this distinction exists at the moment, except that in the first case the changes are not visible at all.