The main issue I see is the Z-axis and the unnecessary weight of it.!

You don't need or want the motor and ball-screw on the front plate because you are just moving around dead weight which will affect the z-axis negatively due to high inertia. Those 180W servos won't handle that weight, especially if your planning on using a large spindle or ATC spindle. You will also need a brake to stop it dropping when unpowered.

Ideally, you want a light but strong front plate with no excess baggage to affect inertia. The ball-screw could easily go on the rear plate and be shorter, the motor could mount to plate coming off slightly longer rear plate. This longer rear plate will also allow more spacing of the bearings which will stiffen things up a little.

The other thing I don't like is the ball-screw on the front. If it was me I'd mount it at the rear out fo the way of chips etc and have the ball-nut mount to the plate which the Z-axis motor mounts onto. Don't worry about the ball-nut not being in the so-called theoretical ideal central sweet spot of the front plate because in real-world the difference isn't noticeable. However, weight in the wrong place very much does affect the machine.