(I'm not sure how interesting this might be or not for most people, I'm just messing around at this point.)
I've been trying a few things on and off and ended up figuring out how to tweak some animations further.
For example, here's X's saber in the original game.
Here's the "speed up" I've done until now: the whole "attack" part of the animation goes on for less frames to make up for the delays at the start and at the end of the animation
This is what I'm doing now: the attack part of the animation is exactly the same of the original game, but the delays at the start and at the end of the animation are shortened.
This was pure trial an error until I realized the way the game stores the animation data allows you to very easily control each sprite's number of frames of duration, or cut parts of the animation entirely.
Here's another example:
Zero's combo in the original game. The "putting the sword down" part of the animation is about twice as long as it was in X4/X5, so it's a lot slower to attack standing still.
And here's that part of the animation shortened to better match the duration it had in past games. It's actually not that much when looking at it, but makes a big difference while playing
And, as I said, you can just cut that part of the animation entirely, making Zero even more op than he already is in this game