While I love the idea of authors being able to fine tune older works there's a bit of a problem in that players will not be able to rescore, rerate, or receive points from older quizzes they've already played, revisions or not. None of the ratings, scores, or difficulties of the quiz will have gone anywhere and, in theory, the older quizzes should be down towards the bottom of the quiz list if they're already of a lesser quality.
While some authors are the type to want to improve their older submissions (and I know some editors and some real-life authors who do the same thing), some may simply find it more to their liking to write completely new quizzes to track their improvement over the years, to benefit from the bonuses you listed, and to start with a clean slate with newer players.
There is currently no system in place to refeature or wipe clean the quizzes of the past; technically, an author could go in and edit one info section, but would it count as a major revision? Authors already do this for correction notices. In this case would it fall upon the editors to designate these particular quizzes?
If it were me I'd opt to look towards the future not simply to add more to the numbers of the site (which is on my mind to an extent) but to demonstrate a visible increase in the caliber of quizzes we place online at the present time. I wouldn't stop people from working on their old quizzes for the reasons you mentioned but I wouldn't want to detract from the value and importance we place on fresh, new quizzes.