Australia has every right to deport non-citizens who commit crimes
The threshold of those who have been sentenced to one or more years in prison doesn’t seem unreasonable
It would be sensible if Australia used some discretion based on the seriousness of the crime, and how long the person has lived in Australia
Ideally the deportation decision and appeal should occur while the person is serving their sentence, so they get deported immediately on release
If there is a gap between the prison sentence and the conclusion of the deportation process, then the person facing deportation should not be held in custody unless there is reason to think they are going to go into hiding
If any potential deportee is held in custody, it should be on mainland Australia. There is no good reason to shift these people off-shore
If you don’t wish to get deported then don’t commit any serious crimes in Australia
If you do wish to stay in Australia and do wish to be a criminal, you should become a citizen first!