The first step is to find an architect and a structural engineer in your area who has done this before. I am an architect who has a practice in Southern California where the seismic zone makes it too expensive for us to design a second story addition that floats above the existing house. Of course it is possible using the technique that you describe or other methods of structural design, but here in Southern California the costs outweigh the advantages for the average homeowner. However, I am always looking for this solution to work for my projects too. It is a great idea.

Wow! Impressive.

Congratulations on your extension. What a transformation!

unable to read all the dimensions but assuming a narrow block of land with zero set back on the garage you would lose extra width upstairs with the additional setback needed for upstairs, none of your examples could fit the available space and there would be a lot of wastage upstairs and down with hallways and stairs and, if a suitable plan could be achieved, there would also be substantial costs ($10,000?) in council, design and plan drawing fees plus costs of living elsewhere for months to build a second story and an upstairs would not improve modest downstairs living and outdoor areas...my suggestions would be to make improvements without over capitalising and could be achieved in stages eg new laundry and move meals storage, (nb this allows the old laundry to continue to function pending completion of new laundry) rearrange bedrooms and replace old external laundry door with window and cladding, enclose the alfresco with insulated wall and cladding), move sliding glass doors and use windows to suit direction of sunlight and outlook in new family room and add a tiny handbasin (inside the wall) to the toilet and, although it's not legal to use a garage for living areas, consider a partition to create a storage area (keeping the garage door) and make a rumpus room with skylight in the garage and leave cars outdoors...these changes creates 4 bedrooms, bigger study, new laundry with storage and a much shorter inside walk to outdoor drying area, generous dining and family room and you could add paving outdoors with a giant market umbrella to replace the alfresco ...unfortunately you will still be astounded at the cost of any changes but hopefully a staged approach would make these changes manageable and you could save more with DIY freestanding flatpac wardrobes, family room and study furniture and your carpenter/ builder might be happy to credit some costs for help with demolition under supervision