These VLJs pose some concerns to manufacturers, insurers and rulemakers alike. Any fat-cat can go trade in his Bonanza on one of these things. But at least processes are being put into place to ensure that said fat-cat reaches some minimal standard.
The 5700 kg thing is just typical of arbitrary points so prevalent in aviation. It may not be just CASA looking at the revising requirements regardless of 5700 kg. ICAO perhaps?
It really needs to be a function of the complexity of the operation, when viewed overall. The aeroplane may be dead easy to drive for as long as it all works well, but speed, high level weather, airspace etc. can be quite unforgiving at times, and when all the pretty glass displays go blank and the autopilot goes on strike, how easy will it be for some people then? I for one don't want these fat-cats tooling around with no proper training and checking. Ergo, those that set themselves up to do said training and checking need to reach a bit more than the basic standard needed to fly, say, a Seminole below 10,000 feet on 200nm sectors. This is not to denigrate those that do fly light twins - such flying has its own demands but does NOT prepare one for a depressurization problem at FL370 on a dark and stormy night 500 miles from nowhere.