With regards to why Squall was renamed Leon, there's some excuse about "he felt guilty for not protecting his world and thus went into brooding emo mode." Frankly, though, there's no real reason for it.Gotta say, I'm actually rather looking forward to you reviewing this one. Had two ex-girlfriends with very different opinions on this game, one loving it and one despising it. It'll be interesting to see a fairly neutral point of view to round it all out.
To be fair, Sora's outfit looks that way because, originally, the game was supposed to be played by Mickey, but Disney is kind of dickish on letting other companies use him, hence why he is barely seen in this game
Though you could make an argument for Tidus' name that TEE-DUS is more derived from his Japanese name, Tida, which was Okinawan for "sun", just as Yuna was "moon" in the same language. Hell, in the Japanese release of Dissidia: Final Fantasy, when all their names are sometimes rendered in English text, it's rendered as Tidus, despite the audio still pronouncing it as Ti-da. And being "sun", it still fits with the weather theme. I do remember the original teaser of X from The Spirits Within DVD a looooong time ago that pronounced it as Tee-dus. Though, I guess I can buy the argument of Tide-us. That's the first I've heard of that reasoning, anyway. Honestly, it can really be just a "po-tay-to/po-tah-to" argument, and with such reasons, either pronunciation is valid.