Ow, ow. Your silly little story, as you seem to think it, is getting intense.
But backtracking. I like how the trio bounce off each other as considering tactics, and the little detail of Yuna's summoner's training. One can tell you carefully considered the nuances of this world. I like how she yearns for Lulu's strategic skills and how Tidus softly recalls Wakka. His attachment to Wakka is almost more poignant than Lulu's to her own husband, at least to me.
Bringing Sin back --intriguing! Will continue.
Author's response
It's silly because I swore I would never write a story with this ending/plot arc, because FFX's ending is so powerful and right that it diminishes its impact to say, "oh, nevermind!" That was one of my chief quibbles with X-2. But sometimes one can't help imagining "what if".
You're quite right about Tidus' attachment to Wakka vs. Lulu's. Although I think Lulu did love Wakka, in her own way, it's just that she tries (unsuccessfully) to bury old sorrows in the past. Also, I firmly believe, the bond between Wakka and Lulu was that of very old friends with a somewhat rocky and imperfect relationship. Very human, very realistic, but not without its problems!