It is obviously very disappointing for you, and anyone would want the new car to function. For what its worth, ive had a fair bit to do with Ineos Australia, and I have found the to be extremely motivated towards all of us, and their work. Thats not to say that lots will go a bit wonky, especially as everything is still a first for dealers and parts chains etc, but they are extremely motivated already to get problems fixed, and their corporate culture really is aware of, and bothered by any situation like yours.
you also have a demo loan car, which, with not enough demos in the country, is a big statement from them towards you. I know you cant modify it or go bush, but… there’s quite a signal of them taking it seriously.
so, going legal might not make a lot of difference to the speed of result, but will of course have some effects, and costs.
i dont know how good the communication is - if there’s a specific part, and it has just not been in the country, then your 3 week problem (you paid 3 weeks before car arrived?) is painful, but understandable unfortunately. It does seem to be rare, globally, that a car is off the road, especially for more than a couple of days, but you are certainly not the only one on the forum, theres a few Since launch.
completely your choice, but patience and understanding, with a good dose of communicating, might get a better long term ownership experience than setting a lawyer into the mix.