Why wouldn't Disney allow it? There's nothing in there that seems too dark for Disney's taste. It would be interesting to have the main bad guys not being Disney characters this time. As far as I know, Hades and Jafar are back.

Beast is also an enemy, as one of the Unknowns has the wilting rose and is using it to manipulate Beast into doing his biddings. It wouldn't surprise me if the Unknowns manipulate other Disney villians in a similar manner. For example, one of the Unknowns could be the master of Jafar, as he is a genie.

With how Another Side, Another Story and Deep Dive look, I'm confident that Kingdom Hearts II will be heavily based off of Square-Enix's characters, rather than Kingdom Hearts which was dominated by Disney characters.