I still say Nami can be out as long as she wants as long as she wants it. Sora and Roxas based it enough that "whomever's outside" is more a factor of their will than who's the "Nobody" and who's the "Heart" (since there won't be a Somebody until there's only one 'person' there, meaning the both of them fused back together).
As for a romance story for Aqua, I donno. I think back to Naruto's Sakura and her romance story was actually the thing that built her character.
Kairi was weak to begin with and because of all the flaws in her world perception just let Sora fight her battles and when those ran out, she was left behind. Let's face it - everyone're asking why Sora didn't stay with Kairi at the end of KH1;
Why didn't she come with him? Hm? No one's asking that, because we all know -
She's useless and will remain like that because she doesn't really care. Har har.
I mean, even Nami for the people she 'cares' for ('cares' because Nomura decided she's a Nobody, hurray for him ~_~) bit her lower lip, braced herself and did what little she could - and got beat up for it more than enough.
As for Aqua I see her leaning more towards Namine and Sakura's side, only yes wielding a Keyblade. She fought pretty well in the secret ending and showed realer emotions when Ven fell off all frozen than Kairi did with her pout and her "I WON'T LET HIM GO!" when Sora all, oh, I donno... disappeared to become a Heartless?
Sweet.
