I would leave the render colour and just tile a trim around the base in a pattern and over the arch of the brick. But I also recalled the pizza oven at a pizza place where I grew up. They make great pizza, but the oven is so cool! You could do something like this!

The façade cost will depend upon the materials you pick and site specs (sloping blocks are a bit more challenging) and labour costs ( just make sure that you check your trades licenses, insurances and references for everyone who works on your house) - once you're structurally sound then the rest is straight forward (it's also been my experience with my builders - who are awesome - that they can come up with some amazing ideas that are cost effective and have a real wow factor). If it were me I'd ask around the neighbourhood for builders that can be recommended - they should be able to do it all at the same time and save you some money. On the materials - I'd be tempted to go with natural timber that will weather naturally without needing maintenance - personally I'd lean towards a Japanese technique of charring the timber so that you don't need to do a lot of upkeep - called Shou-sugi-ban - the reason being that the dark colour will tone in with your window frames.

Your designer should have completed exterior elevations and nominated the exterior materials. Are you looking for assistance with external colour selections, or are you unhappy with your designer's exterior elevation design? Just be aware that not all external materials (such as particular bricks, or stone finishes) can be cost effectively delivered to all parts of Australia. When I am assisting clients I always make sure I know what is available through the local suppliers.

Love your house and especially white houses, I guess if you live on a busy road or dusty climate it will show more dirt, along with that which comes from rain, you'll just have to think of it as more windows to clean. A good hose down with something that paint pro's would suggest every now and then would take care of any staining. Some of my favourites The most famous, just shows that white houses have been around for a very long time, ageless cheers