If the racks move and are as short as you describe, then they would need to be much more rigid than the lead screws. The screws are terminated at both ends to keep everything lined up. With your proposed design, one end of the rack is "floating". To retain the captivated ends, the racks would need to extend 1X past both ends of the printer.
What is the advantage of the racks over the lead screws?
What is the advantage of the racks over the lead screws?
