I want to see AUs with all the other Classic Doctors in the Time War, because it’s a conflict out of time anyways and it might as well have happened to any of them, right?
I want to see what would happen to One, who’s so young and inexperienced, who still hasn’t really shaken off all his Time Lord programming/Gallifreyan upbringing, if he were plunged into the midst of the conflict. Just how averse would he really be to violence? How much would he buy into the party line? Oh, God, what would happen to Susan?
I want to see Two, funny and clever and a little bit childish, forced to fight for the Time Lords. Could the Time War catalyze those flashes of darkness he displayed into something as scheming and powerful as Seven’s manipulative traits? Would he panic as things disintegrate and spin out of his grasp near the end of the War?
I want to see what the Time War would do to Three, who pretends to be a action hero, who wouldn’t have the luxury of being easily ruffled and retreating into himself to sulk during the War, who can fight like a cornered cat for the people he loves and who cares too much underneath it all. Would Three, with his blocked mind and broken TARDIS, be at the beck and call of the Time Lords - or, even worse, be caught off guard when the war stared?
I want to see a terrifying, powerful, alien Four, trying to moralize his way though the decisions he’s going to be forced to make. Would Four take the presidency again? Would he be willing to make the same choice he would eventually make, in a later regeneration? Would he have the right, or would he save or damn the universe differently?
I want to see how Fivey trying to be as moral and kind as Five could be, tired and careworn and caring, and then turn ruthless when the Daleks finally go too far, when the Time Lords finally go too far. I can see Five ending the Time War the same way he would eventually end it in canon, and it scares me, a bit. I’m not sure he would be able to forgive himself after, and I’m not sure what kind of Sixth Doctor he’d regenerate into.
I want to see Six forced into the War, concerned and angry for the well-being of all the innocent beings caught up in it, full of self-righteousness and fury and, underneath it all, deep and desperate fear. I want to see Six bombastically commanding a contingent of his fellow Time Lords against the Daleks and then stopping and realizing what he’s doing.
I want to see how dark Seven could go, how well he could mastermind the entire Time Lord strategy. I want to see Seven defeat the Daleks and stop the Time Lords at their extremes and try to save his own soul into the bargain - now that would be a hat trick - and I want to see Ace right there with him.
Most of all, I want to see how the Time War would change the Doctor, had it happened to him earlier, and how the Doctor would change the Time War. I don’t think either - any of the Doctor’s later regenerations that would branch off after that point or the universe itself - would necessarily be the same afterwards, and I think that’s fascinating.