I'm sorry that I simply don't have the skills to help, but it would be great if this module could support a few Australian services.
Australia Post should I think be the first to get support, but there are others as well: Sendle, TNT, etc.
This, I think, might be the relevant API for Australia Post: https://developers.auspost.com.au/apis
Active
2.0
Code
Shipping integrations are typically done via contrib modules. Unless we have a project requiring Australian Post (or unless it's funded by someone), it's unlikely to happen in a near future (on our side at least).