You know, in reading through all of that, including re-reading the Parafield report, I still haven't seen anything which makes me think that the copper nor RA-Aus got it wrong in the first place.
Take an aircraft that is a little unforgiving at the edges of the envelope, plus an older pilot who may have lost some of his earlier, finer abilities and throw in a couple of gremlins whether they be traffic, weather or mechanical issues and you end up with a good recipe for a cock up.
Yes, shining a bright light into dark corners has revealed some less than desireable critters scuttling about, but they didn't crash that aircraft. I've seen some, who should know better, wittering on about a cascading series of failures making the aircraft unflyable, but I'm afraid anyone who flies behind an auto-conversion or on a homebuilt retract set up, should be able to deadstick the contraption on its belly.
Risk mitigation? Short of demanding some sort of advanced rating with annual reviews (not .4 in a Cub!) for not so top guns wanting to play with demanding toys, I don't really know. I'd hope that if I'm ever in a position to buy myself that sort of toy, that I would be left alone to play and maybe gladden the heart of the odd bystander.