I'd quite like to, either hire a camper, or, hire a car and drive from
Perth to Brisbane. Driving the distance isn't an issues for me, I drive a
truck all day long.

http://www.apollocamper.com/

We rented from these guys..good prices, sometimes GREAT if they want some
vehicles "returned" to their home office.
Also have "cheapa" cars..about 4 years old, in good shape for considrably
less that renting a NEW one. Also good ONE WAY rates (no "penalty")
We used them when available. They also have locations in NZ.

You'll want car insurance. We NEVER buy the insurance from the rental
outfit..its often almost as much as the rental. Try and arrange insurance
from "home"-perhaps your house/car insurance carrier can set something up.
When we went to OZ, we had coverage on our "Signature" level Visa card. I
contacted VISA in advance and they assured me I had full rental car coverage
"built in" to my Visa card. Saved $$

I'm going to mainly use credit cards to pay for things, I can draw cash
(maybe expensive) on my CC. I will take a small amount of A$, but I don't
like to have too much on me.

I 'd never take Cash Advances on my CC..We went for 6 weeks. Used our
Credit Union ATM card (No fees) at Aussie Credit unions to take out $AU.
Never use the exchange booths at airports..they re a rip off !

Any other suggestions, or something I've forgot?

Take a good quality FLY SWATTER (or two) They don't sell them over there
and the flies are very annoying.
Nextime, I'd consider replacing one piece of my luggage with a
"cooler"..just stuff my clothes inside(and take a folded up nylon bag for
the clothes on arrival) for the flight (make sure it doesnt exceed the
Airline baggage size requirements) Coolers ("Esky") are quite expensive
over there and usually get left behind for the return trip.