I do not have experience running a one man AOC in recent years, though did so a long time ago, when we had far less regulation (and no worse safety).
However I have worked in medium organisations where CASA accepted one person wearing several ‘hats’ e.g. HOFO,HOTAC and Ops Manager.
I have even seen the CEO double as HOFO which can be a serious conflict of interest.
To make matters tricky now, CASA’s latest buzz phrase is “single point of failure” - ie a requirement for each post holder to have a deputy to cover sickness, leave etc.
But if yours is a really simple operation (one aircraft?) it should be possible to cover all the essentials with one person, provided that you have some experience in each field.
Assuming that you do have that experience, you may get big brownie points if you voluntarily elected to have an external organisation conduct occasional safety audits and independently investigate any incidents.
CASA really get off on that sh!t.