Intro, 8x4 DIY CNC Router

[GaneshGarud]

Hello Everyone, I am Ganesh from India.
I had completed my DIY CNC Router in last year. (Thank god my cnc parts came from China just before the lockdown).
It has 1000mm x 750mm x 150mm working area, Spindle is of 3.5kw, er20, 220v, XYZ axis attached with Nema 34 8.5nm closed loop Stepper Motor, 1605 ball screw on all axis, PC based Mach3 controller. It was my first attempt to make something completely by myself after finishing my Mechanical Engineering. The machine is working nicely as expected although it has some design issues (Vibrations and Stiffness problem) that I will correct in further upgrade. Please see the attached photos.
I am in process of designing my new commercial built 8X4 cnc router. I am trying to design it as close to the commercially sold CNC Routers.
I never got the hands on experience to any of cnc router. That's why I need some suggestions regarding the specifications details for my cnc router. It will be very helpful if you guys help me to decide the design specifications.
Some assumed design specifications are.
1. Machine size- 5 ft x 10 ft
2. Working area slightly more than 8 ft x 4 ft
3. Spindle 3.5KW, Er20, 220v (Chinese built)
4. Z axis 1605 ball screw directly coupled with Nema 34,
8.5 Nm closed loop stepper motor.
5. X, Y axis 2510 ball screw with rotating Nut type or (Rack
and pinion assembly)( Need suggestions for selection of any one of this)
6. Frame will be made of 3" square pipe with welded structure. Need suggestions regarding gantry design. Should I use 80160 Al extrusion or use MS Pipe. Don't know how the aluminium member will sustain the cutting forces and vibrations. (May it has weight and alignment benefits but I am skeptical). I am searching for the local facility of surface machining and heat treatment for the frame.
7. PC based Mach3 controller, (Is it sufficient or should I use some industrial standalone controller?)
8. Linear Rails of 25mm size for on X,Y axis. Hiwin rails are readily available in my city.
9. Will Nema 34, 8.5 nm closed loop stepper motor sufficient?
10. Rotary attachments for 4th axis. Which drive should i use; belt drive, Worm and worm wheel type or Planetary type?
11. Mathematical design calculations will be difficult because lack of actual design data.
12. I want to use it for woodworking and some non metal cuttings like acrylic and PVC sheets.
I hope you guys will suggest me about the above.
Thank You!