Just out of curiosity: what are you trying to achieve here? What’s the end goal of these improvements?
@TomD has built a gantry-type Maslow that he calls “Mark II”; his goal was to do some flat-ish true 3D stuff, like a rudder / daggerboard. See here: Maslow Mark II - 3D
If you’re only looking to cut 2d stuff, having the sled not touch the workpiece is actually an inferior solution, IMO. The fact that it touches puts your Z-zero at the surface of your stock, no matter how warped it is.
If you’re looking to build a traditional CNC, but in a vertical orientation, your Y axis will need to use a ball screw of some sort, instead of regular steppers & belts. A stepper will not keep your sled / carriage in place when it’s turned off, which was the reason for going with these “weird” motors in the first place.
Also, I don’t think you’ll get much additional rigidity by going “closer” but not touching.
Good point on the friction, though; you’ll probably get a lot more flexibility on the angles with a gantry setup like this.