I have to disagree. With or without Xion, the Org were still lying to Roxas, and Riku still wanted him for Sora. He would have left anyway, for the exact same reasons we thought he left in KH2 before Days was a twinkle in Tomoko Kanemaki's eye.
Old reply is old but I hardly see it like that. The Organization in Days were lying to Roxas mostly about - shock - Xion. Most of what they were hiding from him was - shock - about Xion. Most of the conflict between him and Axel spawned from - shock - Xion.
You can and do argue that the characters were written the way they were BECAUSE of Xion, but way I see it? Without Xion the Organization would've had no reason whatsoever to ever let Roxas out of their sight or even tell him so many lies.
The biggest question here is what would Roxas have done when he'd have Sora-related dreams. Would he do nothing like he did in Days, or would he have became the new Xion in her absence?
Either way though it leaves the Organization for the most part out as a truly active force in the story still.
and Xion, had personality, and some could reason with her, but as a character that was forced to make up the plot, she really didn't do anything amazing.
Funny, this is how I feel about BBS.
My appreciation to Xion and Days as a whole grew ridiculously after finishing BBS and finding out that
They retconned Sora into being Ven, more or less
Compared to that, Days' relative lack of any substantial plot while at the same time focusing on the characters even through ice cream chats feels refreshing.
Most figured out that roxas left the organization due to him wanting to know why the keyblade has chosen him and wanted to find sora himself.
Roxas: but WHY, Axel? ;w;
Axel: you'll understand when you have a Heart
Roxas: .-. ok *smacks another Heartless*
...derp.
I'd sooner say he'd have left because he BECAME Sora from the Memories, but depending on how they would've sugarcoated it, why wouldn't a Sora want to help people for a seemingly noble cause? Without knowing what they really did to people, something they basically threw in his face in KH2?
tl;dr I loved her to bits, I think she's adorable and cute. I didn't mind the quality of Roxas and Axel's characters because I didn't feel like they were OOC and I understand why Riku waited as long as he did to drag Xion back to Sora - he saw her as a part of Sora. Regardless of the end result he couldn't do this, even if she was just a shadow of his best friend.
And lord help me if even half of my theories about how she ties into BBS are half correct.
[/mandatory reply]