2.1 - Instead of replicating the threaded rods, could we re-design around them?
2.2 - Does having access to a printer like this make you feel more enabled?
2.3 - Have you considered the extruder as an application? We can create other 'apps' in it's place, with little modification. Does that give you any other good ideas?
1 - Why can't you use a plastic washer?
You cannot use a plastic washer to replace a metal one. The properties of the washer would decrease drastically, and if was used for tightening a metal nut, it would dig right into the washer. There could be for a plastic washer, but it looked as if they copied a metal washer, for prototyping purposes of a metal washer.