The idea of heading up for 'the season' is somewhat of a misnomer in my experience and is prob more pertinent to the scenic operators. I can only comment on Darwin and the north of the NT but generally the operators are flat out in the wet as roads start to close and govt workers, tradies and locals all still need to get around.
There is obviously a risk to put newbies on during the wet due to the conditions but as companies progress guys onto twins they get desperate for single drivers and so the right candidate with the right ICUS etc should be alright.
Darwin has two or three operators that will take low time guys (Territory Air Services, Air Frontier, Barrier, Top End Tandems and possibly AV8). As mentioned earlier there are also operators they service the remote East Arnhem areas that will take low time guys too (Katherine Av, MAF - if you are a churchie, Air Frontier, Gunbalanya, AAA Charter, Bawawinga and possibly ChartAir).
Good luck, its definately achievble with patience and is def worth it once you land that first gig.