I also doubt that anyone would be able to pull this off in an effective and seamless manner.

Well, maybe just a change in the text crawl could explain the Maul/Grievous connection. It's not like we really need a Grievous with Maul's make up or things like that (although the previous pictures looked great). We can also keep the name Grievous. After all it could be the real name of Darth Maul before he was a Sith. Then, now he's not a Sith anymore, after his fall confronting Obi-Wan, he is called by his real name again. Just an idea.