The plate in question is actually not as much of a mission as described above...although you do obviously need to place the hanger plate over the bolt, it simply clips on (i.e. no tightening required).
It's also a lot safer than the nut + washer + wire solution - once a draw is clipped to the plate it constricts the hole where the bolt slides in, thus preventing the plate from coming off (while being able to swivel around the bolt, good/bad I'm not sure?)
One use for this could be routes in very sensitive areas like the Rocklands
where policy requires that all bolts, nuts and hangers need to be camouflaged (painted). The practice of sanding all the bits rough so the paint sticks is something you'll pay someone else to to once you've done it a couple of times (unless someone knows someone who'll sandblast them for free??). With this you can reduce the effort required and the 'environmental impact' to just having a painted bolt-top and nut stick out.
Added bonus: you get to add another group to hate on and hate from:
Trad climbers can look down on > Hangerless sport climbers can look down on > Hangered sport climbers
Hah! Plus a whole new set of ethics! Fun...