Ventus had no shirt because MX is SUPER cheap. He didn't want to leave clothes to wither away on a dead body. He can trade those for a megaflare or something!
Good thought on why Ventus and Sora have similar faces.
I agree that MX was an interesting character. Even though he was QUITE evil, he still had some good in him. Only Vanitas, in our story, had a heart of pure darkness (presumably). MX was human, he still felt compassion for a failed experiment because that experiment happened to be a human.
Furthermore, while I don't agree with his idea of balance, he really thought he was doing the right thing (at least to begin with). Xehanort's Heartless didn't care, he was doing the instinctual, wrong thing. Xemnas I think also knew he was doing the wrong thing and did it anyway. Master Xehanort truly believed that his goal was a worthy one and that, though his means might be evil normally, were okay because of the end.
I also think he may have begun to lose his sanity towards the end though. It seemed like over the course of the game, his lust for power grew and grew and more of his reason for doing what he did was that, by the end of the game, than his so called worthy goal.
I also loved how in this story it DID present different viewpoints. In previous Kingdom Hearts titles, what we learned about Darkness and Light could reasonably be assumed to be true. It was okay to be in Twilight in this universe, the darkness itself isn't bad, at least, by the end of KH2. However, in this game we see that there really are different opinions on things in the universe, and no one can say for sure how it really should be. Except maybe Sora. Hard to argue with him after he's beaten you to a pulp.
I think the truth of the matter is contained within the story told by Kairi's Grandmother though. I think that originally, the whole Single World was bathed in light, and that was how it was supposed to be. Darkness itself was an aberration. And I presume that's what the story will come back to. But who knows?