I haven't played the Final Mix of KH2... but this boss is a great idea since it's linked to BBS game that wasn't released at the time. (But it's part of the KH2.5.. I think so it's part of the same game for English audience).
I have high expectations for KHIII....
I think we all do, although I'm a little worried about the fluidity of combat. The action seems to be cut off a lot with flashy cutscenes. Sure it's cool looking, but eventually it will get boring to watch. Especially for a Speedrunners like myself, it seems unnecessary. Kingdom Hearts pulled off drive forms amazingly by keeping them flashy and effective. I hope you can at least turn off cutscenes.
Play the final mix, there is no other option. Seriously.