I have been thinking about the stuff that we saw in the extended Trailer from the TGS 2018, and an idea came to mind to explain some of the "nonsense" we saw in the trailer.
1º) First, I have to say, Demyx being a member of the Real Organization is not a surprise. There were very little candidates left to fulfill the remaining places of the Organization. But it really surprises me they pick up such a moron for a Xehanort's vessel.
2º) Second, Vexen however WAS a surprise, especially when they left him along with the others in Radiant Garden, taking only Saix/Isa. However, maybe this "Vexen" is not really who we think it is. In the Manga, Vexen created the "Replica Program" for his researchs, and with it, it created Riku Replica AND several Replicas of himself. So, how about if the Vexen with yellow eyes in this video is actually one of Vexen's REPLICAS?!!!
3º) Come to think of it, there's a high chance that several of the members of the new Organization XIII are actually Replicas, not the real deal. That's why Vexen (or maybe one of his Replicas) has been recruited for the New Organization; to use the Replica Program to fulfill Master Xehanort's objective. Think about it:
+ We have the return of Master Xehanort, with his original body, but this would mean he left Terra's heart and body. Well, obviously, Terra will have to be saved, so Master Xehanort will return to this old self. But how? Well, even if his original body is out there, maybe a Replica of Master Xenahort's body was created to restore his real self.
+ We saw Terranort (Master Xehanort possessing Terra's body) in a very short image, which means it's very possible for Terra to recover his body and release himself of Xehanort. Then again, how is it possible for Ansem and Xenmas to be together at the same time? Well, how about if these two are actually REPLICAS? That way, we can have all characters at the same time.
+ It seems the member of the Organization who attacks Sora in San Fransokyo looks like Riku, but it's obvious it can't be the REAL Riku; especially because it looks like Riku in the first game. However, I don't think this is the same Repliku that we met in KH:CoM, but another one. In fact, it could be a Replica of Riku when he was possessed by Ansem. Since he seems to be controlling the Data Blox, I believe it could be the digital copy of Sora's Heartless, who took the appearance of Riku; or more like "Data-Riku", since it infected him with Data Blox.
In the end, the Replica Program could be useful for the heroes too, because maybe using this tech, they could find a way to allow Roxas, Xion, Namine and other good characters to exist as their own entities; outside of "their original's shadows".
Well, what do you think?
2