Many questions before I build my first milling machine

[iGyros]

Hello guys,
I have worked a little bit on the design again.
I also tried a plan with a fixed portal, but it would be much more complicated.


Here are a few important points that I have adapted.
- The portal is 850 mm wide.
- The travels are about 510 mm x 425 mm x 200 mm.
- Steel profiles with the dimensions 60 x 100 x 6.3 mm are planned everywhere.
- The profile for the portal has the dimensions 150 x 100 x 6.3 mm.
- I plan to use 25 mm linear guides and 1605 Ballscrews.
- Now all support surfaces are underlaid. So far I plan to use 10 mm flat steel for this.
- I made the Z axis much more massive and moved the motor to the fixed side.
- Where it is possible (and useful), I have added angles. These are made of 20 and 15 mm flat steel.
- I have planned a slot table. It consists of a large 10 mm thick steel plate and single 15 mm steel plates for the slots.


I have the following questions.
- What do you think of the Z axis? Does the reinforcement on the "fixed" plate (not on the movable side) give me something or is it just unnecessary weight?
- Do the angles bring me a serious advantage or is that unnecessary work?
- The Z axis plates are 25 mm steel and the reinforcements are 15 mm steel. Is this too thick and just unnecessary weight?
- I would like to mill the angles and the steel slotted table with the machine once it is set up. How realistic is it that I want to mill steel with the machine?
- Which steel should I use for all the components?
- With the size Nema 34 motors (for now) are sufficient?
- I am practically dependent on the 16 mm ballscrews, because I would have to mill too much with the 20 mm ballscrews and I currently have no milling machine. At work a college can facemill the all mounting surfaces, but unfortunately they can't do too much for me there. Would I have a big advantage for 20 mm ballscrews?

What do you notice about the plans? Are there any more mistakes somewhere?