Feedback on DIY 3DP

[Spixe]

Hello!

This is both my first post in here and my first 3D printer build. I started from rock bottom and have read quite a few articles about 3D printers up until now. I have access to stainless steel mainly, so this is what I have been thinking of making the printer of. The design I created in SketchUp is not final at all, and dimensions of shafts and so on are not known yet, so they are just examples.
- The print dimensions of the printer will be about 200x200x200mm.
- I'm planning on using that San-something controller board, since I do not own an Arduino.
- I am most likely going to invest in some Nema 17 steppers.

My concerns:
1: Does the design work?
2: Will the printer be too heavy? I will try to make the moving Z-axis as light as possible, since it has to move up and down.
3: I am aiming to make it fairly sturdy, so I can use it for engraving as well (in metal hopefully) and maybe milling in wood.
4: How important are heatbeds?
5: How big stepper motors would I need for my design, considering it might be fairly heavy compared to normal 3DP's.
6: When buying stepper motors, should I aim for high voltages and low current (ex. 12v, 0.4a) or the opposite (ex. 3.4v, 1.7a)
7: Anything else I should be aware of?

Here is a screenshot of the printer sketched in Sketchup. I can upload the 3D model to the warehouse at some point, if it makes things easier:
http://peecee.dk/uploads/122014/Unavngivet1.png

Oh. And I do not know if this is a the correct category at all, so I hope I am not too much inconvenience.

Thank you all in advance!