If I was in the movie business, i'd of made a sequel to ST6 as ST7 and done generations as a standalone first movie for TNG but it would've been different.
I've long felt that if Rick Berman had a little more
vision, he should have held the crossover film for the 30th-anniversary in 1996 and done a standalone original series film in 1994 that also set up the crossover film. But Hollywood didn't do "big picture" thinking like that at that time; that's what made Peter Jackson's
Lord of the Rings trilogy so surprising and so risky.
Back to the original idea in the thread, I think there are ways of making the film prologue work with Sulu that also would have dealt with Takei's concerns.
Let's suppose you have a trio of Kirk, Sulu, and Scotty, and Demora is Chekov's daughter instead.
Everything goes as we see it... until Harriman realizes he needs help and he turns to Sulu, the active duty officer, instead. Or he turns to Kirk who defers instead to Sulu, the active duty officer. From that point, Sulu has Kirk's lines and when it comes time for Sulu to go down to deflector control Kirk jumps in and says, "No, I'll do it."
It would work. It would emphasize that Kirk feels a bit useless since he's just a spectator to all of this, but we would also lose the subtle touch of Kirk
almost sitting in the center seat before he decides to go to deflector control.
Would this have made Takei happy? Who can say? Does
anything make Takei happy? But it would have addressed his concerns about Sulu's apparent "demotion" by making him more central in a way that also emphasized Kirk's arc.