Pay two thirds of mainline - not such a simple statement, 2/3rds of whose pay (senior, junior, permanent pattern line or rotator??)? For the junior guys the pay is effectively equal, if not more in some cases. Throw in Cairns cost of living versus Sydney and it can be lots better, i.e no loss of money through rotating as a junior guy.
Commands - They are accepting expressions from non B767 Captains to be trained on B767. After that they will look at upgrades. Part of the decision process of the individual will be command issues on return to Qantas, those who do get Command upgrades (if this happens) will try and time their length of contract at Australian (initial contracts vary between 2 and 5 years) such that they will be eligible for command on return. Regardless, isnt 5 years command at Australian better than that time spent rotating as an FO in mainline? (for those interested in Australian).
Yes you do have to make your own way to Cairns.