More Namine scenes 
QFT.
What I'd change is that I'd make it clear that Naminé didn't "replace" Kairi in Sora's Memories. SoKai y/n aside, the possibility's plot value always seemed all but meaningless to me. If they really wanted SoKai, they should've written it better in KH1 instead of let Watanabe write a whole new couple that would spin a whole game around it just to later say "lawl SoNami -> SoKai". Also, it would've kept me from going "SoKai? Ah, it's because of SoNami", seeing how the two couples would've been unrelated, thus increasing SoKai's debatable value in KH2.
Naminé began from being
another girl. She was not Kairi, she was separate from Kairi, and later on had her own interaction with Sora and Riku that is different from what we know Kairi had with them.
The moments that dictate Naminé and Sora's relationship the most are moments that Kairi never would fit into (until of course I'll be proved right about Sora's "you've changed, Kairi" comments as being the truth and that KH1 Kairi is different than the Kairi he grew up with which was more Naminé like), starting from her being unlike Naminé in personality, to downright being away from DI when those Memories "took place" (the Promise Memory, durrrr, ya know, it being on the night that Kairi only
came to DI?).
Naminé being lonely for her entire existence and then bullied by the Organization, imo, would've made for more than enough motivation for her to create herself in Sora's Heart, as well as her being a Nobody at all, not necesarilly Kairi's.
Also, her telling Sora that Kairi is his most important person. Again, me calling Shenanigans on it since if KH1 managed to convince me Sora cared about Kairi at all, it was hardly as his most important person (that always seemed to be more Riku's role until Naminé as Naminé came into the story) aside, it's all but unbelievable.
Sora forgot
Riku, who was undeniably based as Sora's best friend and the person he'd do literally everything for. He forgot
Riku, and everything else, so why should I believe it full heartedly (if at all) that when the Good Luck charm changed back into the one Kairi gave him, that it wasn't changed back
by the person who changed it originally?
By that point, Naminé was determined to save Sora - even and probably specifically if it meant getting his attention away from her. Naminé changed it to begin with, so now that Sora was all but obsessed with her,
she changed it back to try and convince him otherwise. Yeah, and this is supposed to base SoKai to me how? It just shows how desperate Naminé was about Sora, and how stubborn and desperate Sora still was about her.
Now I know Sora had to "remember" Naminé and have a somewhat physical embodiment of her, but seeing how he forgot
everything which was
not Naminé, the Charm could've changed back and brought along with it Memories of a lot of other people he left behind, not only Kairi - much like Riku's
Destiny Islands Keyblade materialized from his Memories when he met Kairi. Naminé thus reawakening that part of his Memories - especially after he was in DI and we saw that no, he barely remembers even that world, would've been much better played imo, and gave Kairi a proper meaning instead of something gag-worthy.
Now inb4 the Kairi-hater-haters, if you'll reread this, you'll realize that I was actually saying they should've written Kairi better and took away from me several excuses to write SoKai off as "blamed" on SoNami.
Har.
