I haven't played days yet, so I don't know alot about the personalities that make up the organization, but I want to know ur opinions on the members true natures:

Did Xemnas ever really care about any of the members? Do you think that even if he did create a world in his image he would help them get their hearts back? Or do you think he only needed them for fighting force?

Is Demyx a good guy, but too cowardly to go against the organization? He's working cuz he gets a heart out of the deal?

What do you think Marluxia was planning to do when he took over the organization with Sora's help?

And anything else related to their true motives.

No, Xemnas didn't care about any of the other members, even his old comrades (the other 5 apprentices). He just wanted to create a new world for himself and reign as a god over that world. I doubt he would help them get back their hearts, because then they would lose all of their powers and be of no more use to him.

 

Demyx is, like most of the Organization, just a neutral person. He isn't good or bad, he's just heartless and doesn't feel like doing missions because he's so lazy. I really doubt that he cares about getting his heart back, but since he's such a minor character, we can't really make out that much of his motives or personality.

 

Marluxia just planned on taking control over the Replica Plan and overthrowing the Organization using the Plan's findings as his own miniature army, along with Larxene and the Namine-brainwashed Sora. It's never really stated why he wanted to do this, or what he would do once he succeeded, but I guess he just didn't like going along with Xemnas' ideas and wanted to become more powerful than the other members.

 

As for the other member's true motives: Xigbar seemed to have more going on than what meets the eye. He'll be back in Birth by Sleep, so it might reveal what he was up to there, but I honestly have no idea. Xaldin, Vexen, Lexaeues and Zexion were all loyal subjects, so I doubt they had any hidden agendas. Meanwhile, Saix and Axel just wanted to get back their hearts and made a pact to do so when they entered the Organization together. Demyx, like I said, probably didn't care either way, although Luxord obviously wanted his heart back too, from his actions and loyalty towards Xemnas' cause. Then Marluxia and Larxene just wanted more power, and Roxas just wanted to know who he really was. All in all, I can say that most members just wanted their hearts back, but decided to go about it in their own ways (i.e. Saix, Axel, Roxas), while others wanted something else (i.e. Xemnas, Marluxia, Larxene).

I don't really know. I'm sure everything will be revealed sooner or later.