The only reason why I worry about such a lopsided idea being enacted is because of the support it has been getting elsewhere- already deployed in France and Germany as a 'tax rebate' style operation and it has plenty of momentum behind it in the UK and US.
On the odd chance that something like it actually happened, parts and vehicles would dry up very quickly for the owners of ancient Japanese cars. It'd be nice if it stayed hot air but there is too much money behind the ones lobbying for it for me to sleep easy.