What about remaking the whole serie as a trilogy? That proposition is weird, but they could fuse KH1, Chain of Memories and days under the same game and remove all the tedious repetitive gameplay. Then kh2, bbs ans recoded as the second remake.
And finally ddd, 0.2 and 3 under one story narrative.
That would be weird but with some tweaks it is possible.
That's an interesting idea, but I'm not entirely sure how you'd pull it off. They are all their own stories and partly have their own main characters. You'd have multiple climaxes in one game, which might just feel odd.
You'd have to rewrite the stories quite a bit, having your protagonist switch all of a sudden would feel weird. Though I can see potential ways of doing it.
While merging it into a trilogy does seem harder, I can see some of the smaller titles combining and some of the bigger titles absorbing smaller ones as prologue or epilogue.
I can see them merging CoM and Days. the game starts out with you being able to play as Roxas, Sora and Riku and after CoM concludes you'd swap out Sora for Xion, with her taking over his stats.
I can see Coded being combined with KH2 as a short epilogue chapter. Data!Sora would just share his stats with regular sora and the revisiting of the worlds would be truncated and not repeated 3 times.
And 0.2 could be used as the framing device for all of BBS, it being the story Mickey tells them not just the 0.2 part, with it just continuing into the regular 0.2 past the final episode. Obviously we'd experience the events in more detail than Mickey tells them. Like Mickey will say they saves a little girl at radiant garden, but not know it was Kairi.
A seriously truncated version of DDD could be used as the prelog for KH3, though I can't imagine anyone making 7 new worlds just to rush through them for a prolog. But maybe a End of the World kind of thing where you enter 7 rooms styles after the various movies, maybe they'd manifest as different districts in Dream Traverse Town? But you wouldn't really bond with Dream Eaters and the introduction of the TWEWY crew would feel weird if they didn't reappear in the later game.
Now I kind of feel in the mood to give a Darkseeker Saga rewrite another try.