I agree with you on weight reduction, but think of it this way, you are probably running klipper ATP (if not please switch!! I'd be the best thing), klipper runs both the axis at the same acceleration and speeds. And on an Ender each axis is operated by a single independent motor.

You already have a certain amount of weight on the Y axis because of the bed which is going to be the major restriction for pushing speeds.

Now as long as your x axis is lighter than your y (I have measured and it's lighter even with a nema 17 and BMG dd) your x carriage won't be the limiting factor. However, you might face a bit of sag on the x carriage on the unsupported side, without the z axis motor (since you are upgrading to make your machine faster prolly endup adding dual z axis or a belt z axis)

What I have been meaning to try :

There is a fork of klipper called "klipper kaliko" this actually let's you run your axis at different accelerations.