Twilio developer evangelist here.
For phone number regulatory compliance there is the concept of an "End User" in a system. The end user can either be your business, in which you only need to set up a regulatory bundle for your own business. Or, there may be several end users who are your customers. Those end users can be individuals or businesses.
In your case, it sounds as though part of your business is making phone numbers available to other businesses. So, in this case the other businesses are the end user of the phone number. You will need to get those businesses to create a regulatory bundle before you can provision an Australian number for them. If you have 100 customers, then you will need to create 100 regulatory bundles.
There is an example of creating a regulatory bundle for a business customer in the documentation. That is quite a manual process, if you would prefer to make the process available to your end users instead, you can use the regulatory compliance API to create a portal that allows your end users to upload their own documents.