Box and V ways aren't wheels, and neither of them are extruded. They're usually cast iron and ground to shape. I'm positive you would have seen them on subtractive machines. Second picture down shows some V ways on a lathe bed: http://www.lathes.co.uk/okuma/

For the record, the two steppers I'm talking about is not two separate steppers, attached to two separate leadscrews. It's autowiz's idea of putting a stepper on either side of a closed loop of belt instead of having an idler at one end. Having two steppers on two separate leadscrews for Z is better than a cantilevered setup, but still not ideal. They can get out of sync, especially when power is off and the motors have no holding torque. Or if one motor skips steps etc it skews your X axis and you'll need to re-level it. ideally you'd couple the two leadscrews together so they stay in sync (say, with a belt) and drive the belt with a single motor. You can "fix" the issues by having two z homing switches, one for each motor, but most people don't. At that point it's just as easy to couple the two leadscrews and drive it all with one motor.

And autowiz. Just because you printed an i3 doesn't mean a thing. Lots of people have done it, and a lot of them just like you don't understand much if anything about design. Wiring two stepper motors together will not cause a house fire, I don't know what makes you think that, neither will a solenoid relay when used properly (you know a lot of your house appliances use them? Like ovens, boilers and more? Including resetable circuit breakers which help stop house fires?). What makes you think car parts are made to start house fires? Did your car burn down your apartment? You know the real fancy control boards like the rambo which have actual fuses for safety? Those are automotive fuses.

Also, steppers are not fancy servos. They're brushless motors "optimized" for holding torque and positioning accuracy and repeat ability with open loop control. Servos are the "fancy" ones with closed control loops and feedback. The pot on the driver board controls the current to the stepper, not it's initial position.