If you look around the world, Tecnams, Sportstars, Pipersports, Skycatcher's and the like are registered as per that countries normal aircraft registration and carry that countries normal registration ie in the USA 'N'. Australia is unique in having a separate body issuing aircraft registrations and pilot certificates.
To move forward RA-Aus needs to change and one easy step would to allow PPL holders and above to be able to fly an RA registered aircraft without the need to be issued a separate pilot certificate. By dong this, it would reduce the administration burden and reduce costs.
The argument about the light weight and or high performace of same RA aircraft is stupid, as just in the GA world, before any school will allow you to fly one of their 172s, PA28 etc you are required to do a check ride for insurance purposes. So the GA pilots will expect to do the same before flying any RA aircraft.