Your age is a problem, as I'm sure you are aware, however employment opportunities for mature age apprentices are rapidly improving. Employers still have a problem with $268 per week for a 17 year old apprentice, versus $480 per week for a mature age apprentice. This year the Queensland Government increased funding and subsidies for mature age apprentices, which may work in your favour.
I suggest you first talk to the manager of their Group Training division. Between he and the general manager of the RTO, they have broad industry knowledge and contacts and should be able to assist you obtain employment.
I think you are shooting too high - I'd forget the airlines for now. I'd do the rounds of the GA and regional hangars as I suspect you will have a far better chance of gaining employment and you will learn the industry and gain your LAME license in a far broader and more diversified environment.
And if all that fails, send me a PM, however I can not assist you with apprenticeship employment in the Brisbane area but may be able to assist elsewhere in Queensland.