For Grievous=Maul, my idea has always been to have this revealed to Obi-Wan on Utapau, in the close-ups of their eyes. Taking one of Obi-Wan's two "It can't be"s from the security hologram scene would sell it, IMO. A voice actor would be required to dub over Grievous and whatever lines Maul might have in our Episode I. Grievous' Episode III dialogue would make or break this connection, so it needs to be top-notch. Also having the Nemoidians refer to Maul as Grievous in Episode I. I think we all like the name Maul better, but there are just too many characters who refer to Grievous by name in III to get around it.

As for the duel, I actually have a rough edit of an uninterrupted Anakin/Obi-Wan duel I'll upload this weekend. I think it works rather well, but in the context of the film it would probably be best to cut away at least once. Who knows, that's a long way off. Anyway, hopefully it'll be up by Saturday.