Thanks for all the feedback everyone.
In defence of our architect, he really met the design and layout requests of our brief. The garage really doesn't work positioned on the western side of the house - we need rear access through the garage and that position cuts into our tapered land and makes our yard less usable. There was also issues with the articulation zone and boundary line if we positioned the garage to the West.
The study is actually a home office and we do require it at the front of the property. And having lived in open plan homes, hubby and I can actually justify a media room - we're avid movie watchers and would like the separation from the open plan areas of the home. We don't currently have plans to put a TV in our open kitchen/living/dining space.
I would say we could reduce size by not having an upstairs living space - but hubby is adamant about having additional living space vs a hallway to bedrooms.
We both see the benefits suggested by reversing the design and having living spaces upstairs, but it just lacks practicality for accommodating our large dog, toddler, ease of access to our backyard for entertaining and also our elderly parents.
We had considered having a door that closes off the open plan area from stairs, but will look into ways of blocking the stairs.
As I said in an earlier reply, we felt like we're in a position where we have to balance our expectations. We didn't begin our knock-down-rebuild journey with ANY understanding of sustainable and efficient design. I actually read the My Home website before seeking advice here, but without a mechanical mind, I'm hard pressed to understand its intricacies.
And then we have our budget constraints. So our goal is to look at the best levels of insulation and double glazing. In terms of heating and cooling mechanisms, that will also boil down to cost.
I think this thread just illustrates the underlying preferences we have when approaching this build. Without all the money in the world, we have to channel it towards our needs as a family. Considering our current home has NO insulation in the front portion of the house, a ridiculous amount of windows facing East and West with no shade or glazing and no space for a fridge/freezer that meets any energy efficient rating... Anything will be an improvement.