xion's image

[Smile]

He may have used the data from that event to begin to build Xion, but the finishing touches were the memories of Kairi that the Organization steals from Sora while he is in the Memory Pod.

Lol what? Xion looked like Kairi long before Sora went into the pod, be it because that was what Namine delinked first, or because it's actually a twist and we're dealing with Xion being a Namine clone and not Kairi copy. And by the time he went into the pod, all of his Memories began leaking out, with those of Riku making a stop inside Roxas, and the rest moving into Xion.

Personally I don't think Xion was composed of any data gathered in Xemnas' encounter with Sora. In Castle Oblivion, Vexen was able to secure data from the real Riku to shape his replica. The Riku Replica was an exact copy of Riku with a copy of his memories.

..Riku's memories were copied as data and implanted inside the Riku Replica

Only the very next day is when Xion was brought into the organization. Funny coincidence.
Also, you're forgetting the reason Repliku had a copy of Riku's Memories was Namine. Repliku originally had none of Riku's Memories. It wasn't until they forced Namine to go to town with Repliku's Memories that he had Riku's Memories.
Namine could've copied enough of Sora's Memories that involved Riku, or simply copied them off the real Riku once he reached the Castle. Both would leave us with that as an invalid example though.