Well, that makes sense. But then Padme could never be too pregnant throughout the movie till the end. Even 9 months isn't very long to kill all the Jedi masters yourself, and she's pregnant when she meets him on Mustafar. Making the babies come sooner would not only mean shrinking her tummy, but also explaining a number of plot difficulties, such as why she'd fear have the babies without him knowing, why Obi-wan is present, etc. So I guess a storyline like you indicate would mean aalenfae would need to shrink her belly for much of the movie.

While detracting from the Ben/Ani climax, it still seems easier and more justifiable to include at least something in the end (I would imagine a several year project hunting down the Jedi). Perhaps Order 66 would remain where it is now, albeit given by Anakin instead of Palpatine, and of course a tad shorter. Then have armored Anakin/Vader continue killing off more Jedi afterwards. This way many of the Jedi wouldn't even know who their assassin really was anyway, maintaining the galactic mystery of, "Who the heck is Palpatine's new henchman?"