Your money may be better spent on making that a feature to the bathroom & study & internally with a window as the nice focal point since it is due west. Small bedrooms won't matter so much with improvements to the living rooms though you might be able to bump them out under the eaves but slab homes don't usually extend the slab beyond the footprint. Then extending the living area towards the east to introduce the interiors to that beautiful aspect, despite the drop off of the yard maybe singular addition is cheaper than knock down of interiors & plumbing etc. Might be able to step down a few steps into an amazing living room????? I would be mindful of what you will see when you walk in the front door & if it could see through to the yard that is always pretty cool! Piccy just for inspiration...

Yes, this is very much a 'how long is a piece of string' question! And the answer is probably very much a 'you get what you pay for' answer! We have just built a house and paid in the vicinity 0f $1800/m2 - the builder we used has 3 lots of 'specs' for houses - basically the lower budget, the middle, and the higher end. For our given floor plan they could quote on each of the specs and we went with the middle one. This involve things like the quality of the fittings/appliances etc. eg. with the low spec we would have got a basic kitchen with formica benchtops, the middle spec included soft-close drawers and hinges with stone benchtops etc and it was the same for all the fittings throughout the house - toilets/vanities/laundry fit out/quality of carpet/type of concrete for drive etc. A word of warning - we had a friend who was very happy because he built a house for just over $1000/m2 - but you could tell! It looked all fine when it was brand new but after a few months you could tell the poor quality of some fittings. And the carpets were already looking worn! so - you get what you pay for.

Sounds like this house may be a money pit and you are just making new of existing problems and not in the end getting a better result. If the house was in good order and you only needed to knock out say a wall or two to open up the space. Or also possibly replacing the kitchen and bathroom and finally giving the house a fresh coat of paint (inside and out). It may be work considering and speaking to a builder and bathroom/kitchen designer to get prices. But if the house needs much more than this it may be better to look at demolition, (see a builder about this) then rebuilding a prefab or kit home to suit your current and future needs. From my experience any old home that needs major maintenance work completed and also room reconfiguring is a much more expensive project to take on then building something new from scratch. If you do decide to go down the building road, then I suggest working with a good builder who has great communication skills and pick a knowledgeable interior designer that does more than pick paint and tile colours. You need a designer who has a rough idea, (based on past experience and similar projects in your area) of what things cost. Set them a reasonable budget and get them to pull together ideals and concept drawings so your builder can give you a pretty good ball park cost. You can alway pass then next stage onto a draftsman if its not to complicated and work with both the designer and builder to find the correct balance to meet you personal style and a budget.

Always check with your council, they mostly like to get cars off the street in the city if the can. It is a great looking house and will be made to look even better when the car yard can be moved to the R/H dead side of your house. Don't do something because it's the cheapest, have a plan and wait until you do have a few spare dollars. It will add big value to your property With 4 cars it looks like you could call on some family man power to do some of the work, and if you have family or friends with trades required to do the job, throw a BBQ but no food or Beers until the works done cheers