Formed steel cnc router

[sbams]

Hi all

i want to start a build log for my first DIY cnc machine.
the construction will be all formed steel welded together.
1/4 plate for the table and 3/16 plate for the gantry. There are still quit a few gussets I will be adding I just wanted the start this log in case I'm way off.
3/8 plate for the main bed and bolted on 3/4 aluminum plate for the cutting area bed.
The reason for the formed steel construction is I can build the whole thing from scrapes at work and not pay for the steel. and I can cnc plasma cut all the parts
the cutting area will be roughly 15" x 15" x 5".
all rails will be 20mm profile
X and Y ball screws will be 1610 with 2.1 pulleys
Z ball screw will be 1605 with 2.1 pulleys
i have Nema 23 motors drawn but not sure if there big enough (one of the questions for you guys).
i want to cut aluminum and stone mostly but I imagine I will cut some hard woods as well.

questions:
How does the design look so far? Will this cut aluminum or am I dreaming!!
Will the Nema 23s be strong enough?
are the pulleys a good idea or should I direct couple them?
what step angle (degrees) is recommended?
i know I will have a lot more questions along the way so thanks I advance for any help.