Prior to SOO there were interstate games between NSW and Queensland, in which Queensland players were turning out for NSW because they played in the Sydney competition. These games were usually one sided affairs and nobody was interested in watching them - which was why SOO was introduced in the first place! The original concept was simple enough - if you played your junior football in NSW you could play for NSW, if you played your junior football in Queensland you could play for Queensland. If you played your junior football in England or New Zealand, you couldn't play for either. Nor should you!
It isn't origin elegibility that's the problem, it's the absence of any meaningful rules in the international arena. If you are born in another country, you should be able to represent that country. If you come to a migrant destination like Australia as a child, and learn your junior football here, you should be able to represent Australia - but not both! Your country is not just another club that you can leave if you get a better offer.