Honestly I'm hoping they do a new theme song for the TV series. Either by Utada or another singer
They can't just throw "Simple & Clean" into the bin! That song deserves some respect. They need to use it at least once! I can see "Dearly Beloved" being the credits music.
I can't see a brand new song being used, it would just not feel like KH1.
If it is based on KH1, I could see them potentially doing what Persona 4's anime did for its first episode, have it’s intro be the Simple & Clean remix and have its ending be a new song used for the show’s proper intro theme. After that, they could use original songs for the show's openings and endings. Then for the final episode, use the original version of Simple & Clean for the ending.
I don't know what Personal is, but I wouldn't mind the first episode using "Simple & Clean (PLANITb Remix)" as the intro and actual recreate the KH1 intro. Then other episodes can use different songs, maybe Utada can make an entire album of theme songs. Each episode is a new Utada song for the intro and another brand new one for the end. Then the last episode can use "Simple & Clean".
I’m very curious if they’ll include anything from Secret Episode/0.2 before the actual Birth by Sleep season. It would make sense timeline-wise if the series occasionally shows what she was doing, especially involving KH1. But would it be a discouraging spoiler that ruins the ending of the upcoming BBS season for the new audience? Or would seeing any part of Aqua’s journey through hell just be too confusing to show for an audience that doesn't have BBS knowledge?
I’m trying to imagine the discourse of her first appearance on Disney Plus. Who was that sad woman? How did she even get in the realm of darkness? What was she talking about, something about a Ventus and Terra? Huh? Wait it took Mickey THIS LONG to finally find her???
To reference what I said above about recreating the KH1 intro. I think they should acknowledge or hint some things that are to come - like Ven and Aqua. The KH1 recreated intro can easily be reconfigured to reference Ven's heart somehow, as the KH1 intro itself is so abstract that if I look at it now, I can probably find something and say "that could be a Ven reference". They can have stuff like Hercules/Peter Pan saying that Sora reminds him of someone. I would also love to have Hollow Bastion a little bit more detailed, where we can see a Xehanort painting in the background and maybe come across Aqua's armour (since Hollow Bastion is in the "ruined" state in KH1).
They shouldn't be afraid to write the anime series the way that the story should have been told IE written by Nomura with all the knowledge of the story beforehand. Nomura made up as he went, so things kinda had to be stitched together manually with each passing game. Now that the whole story is out, the anime should show us stuff that reasonably should have been in KH1.
Regarding Aqua, I think it all depends on when the BbS season will be. I'm not sure how well it would pan out introducing Aqua in Season 1, then having to wait at least until Season 4 to see her (Season 2 = CoM/Days, Season 3 = KH2). They could have an after credits scene with Riku/Mickey in the Realm of Darkness, where Mickey says that he wants to find the keyblade wielder that was helping him - which then causes Riku/Mickey to get split up for CoM.