I just read your list of Questions and Concerns, and I think I can address number 6. When they first brought up the seven lights and the thirteen darknesses, my original thought was: “Okay, so the seven lights are Sora, Riku, Terra, Ventus, Aqua, Kairi, and Mickey. And the darknesses must be Organization XIII!” I was, like, two-thirds correct on that assumption. But it turns out that the seven lights are the princesses. So I think that Mickey or someone else will spend the next game gathering the princesses, and putting them in one place. Each princess will be assigned a guardian, which will be one of the Keyblade wielders. And, they might even have certain guardians protect the princess that they have certain history with. (Like, Ventus or Terra would protect Aurora, since Ventus thought she was the most beautiful woman he’d ever seen, or Terra since the Enchanted Dominion was where he first began to sink into darkness. Aqua would protect Cinderella, since she had a big role in that world, etc. Kairi is difficult to predict, though, since she’s both a princess and a wielder. But I’d guess that Sora or Riku (or both) would protect her, until she decides she doesn’t need protecting anymore.) Yen Sid says in the secret video that a second Keyblade War is going to be unavoidable. Xehanort is going to attempt to use the princesses to make the X-Blade, like he did with Ventus and Vanitas. I believe that the reason they’re settling for the defenders of the light is because they’re going to literally become defenders of the light and protect the princesses in the upcoming war.
I really like this idea! I think this could easily end up happening. Unfortunately, the more I think about it, the more I see that they are just using the princesses as a motivator for them to assemble 7 key-blade wielders though. I think in the logic of this universe, it ONLY makes sense for Xehanort to use the princesses, but they’re ignoring that fact in favor of making a sort of “Avengers Assemble” initiative with our seven soon-to-be heroes, saying “Well if we don’t fight he’ll just kidnap the princesses, so I guess we have to fight.”