Seems to me like another misguided effort by polititians who live in fairy land to punish the many because of the few idiots who just do stupid things.
Fixing new seats into a car without a mod plate does not necessarily mean that the car is defective, it just means you haven't paid a fee to the government to have someone to say it isn't defective.
Its idiots that chop and hack their car to fit accessories without concern for safety that make it hard for genuine modifyers, and have brought about the need for the mod plate system.
You never use to need a mod plate in queensland for fitting factory options to your car. IE v8's into 6cly and bench to buckets, but because of idiots who did stupid things and took short cuts, now you do and you can be defected for it and have your car taken from you.
As i write this i am reminded that these are the same type of idiots who cant wait for the rain to make the roads wet so their car will spin the wheels because it wont do it in the dry. Pathetic.
Its this kind of behaviour that causes accidents and deaths and forces the government to appear to do something, or anything to stop it happening reguardless of its actual effect. They're not into cars and dont give a sh#t if you are.
Think about it next time you do a skid or have a race or chop your car to modify it, eventually it comes back to bite you on the ass, like whats happening now.