I personally think the cladding would look nice and be the easiest to maintain. We also live on the Gold Coast and have a brick house that has been rendered (not by us) and, to be honest, it is not particularly low maintenance (if you want it to stay looking good that is). It is prone to leaching which leaves ugly stains so regularly needs retouching with the paintbrush. It can also develop small cracks in the render due to temperature change and movement. However, the most worrying thing for us is with regards to termites. If you render over your brick on the lower half of your house, it is highly unlikely you will see the telltale "mud" they leave that indicates they are trying to gain access into your house (they climb up in between the render and the brickwork). I would be trying to keep the exposed bricks in preference to rendering over them, particularly if you have a garden bed up against the house anywhere.

For a cheaper, faster and possibly easier option, take a look at this for some inspiration. The lighter colour of the walls may reflect more light and be a stand out feature of your home. Click on the link and scroll to the image of the polished timber floor with the timber wall and ceiling. Polished timber floors with timber wall paneling

We want something that blends in, but because it's a zinc and colourbond shed home, I want to choose a colour that makes it look more like a house and less like a shed. I was looking at basalt but my husband would prefer a lighter colour for keeping the place cool in summer. My original choice was windspray but I'm a bit concerned it won't contrast enough with the zinc roof...but perhaps better than dune that might look too 'sheddy'...so hard to decide!

Look at 'Iron Ash'. Its a treated version of what you're after. Don't know anything about it but seen it recently on the web. Overall avoid Merbau as mentioned above, as well as being an imported 'sustainably' managed timber.... Use local product's when available as they're manufacturered to high standard's, supporting local job's, companies must meet tight regulation's, etc. unlike other countries....