Hi, a big house but for me a few issues

1. Stairs. Awkward to access from front of house. You have to start stepping down into rear space and turn to go up the stairs. I would reverse the stairs. Which will make it easier to take unending to laundry too.
2. Lack of general storage for linen, and general household items like sports, decorations, etc. you could move door to bed 4 and put cupboard in that recess
3. Upstairs rumpus is narrow, suitable for study and perhaps a small table to play games etc.
   4 laundry sink I would shift it a little from window so you have a bit of bench on both sides. Same goes for sink in kitchen. In fact I would hate to have too be stuck in butlers pantry to wash dishes.
4. Alfresco is pretty narrow for dining
   6 pool, 500mm between pool and fence is too narrow to comfortably walk beside pool. You need a sitting area instead fence to allow supervision.
   8 vanities in all bathrooms are small lacking bench space. Add niches, shelves and recessed mirrored cabinets to help. Showers will need doors to contain water
   9 master bed 2. How will you add curtains to the corner window with the bed there? Why twin beds against wall? And add door to wir.
5. Master 1 ensuite i would make larger. The bedroom is massive by comparison.
6. The only bath in house is in master bed 2. Is that practical?

One my thing, I would move door to media to entry hall. Gives better privacy to guest room and allows you to hav a grander entry to the room.

The garage space is too small for any suv or 4wd. Should be 6m deep or wide. There will be not enough space for walking around vehicles and comfortably opening vehicle doors. The downstairs powder opens to the family room, this is not private. Have redesigned so the door opens from the mud room hallway. Then toilet will be accessible for pool users by going through the laundry from outside, instead of running through the family kitchen area. You will need a underbench beverage fridge in the kitchen for everyday items, milk, cold water, etc etc. because your fridge is hidden in the butler pantry. Where will you make your tea or coffee, where will you prepare your breakfast. Personally fridges are better in the kitchen area, not the pantry. You have so much space for clothes storage with the WIR, but where is storage for linen, towels, bedding?

Walk-in robes are often more of a waste of floorspace than a genuinely larger storage facility.

Do the secondary bedrooms need ensuites? Apart from the obvious questions, that's a lot of hot water pipes and associated inefficiency.

If you want space to move around, the important area to include that is in the suite which will be used by the oldest members of the extended family. It makes no sense to have large and grand WIR's for example, but have a situation where one occupant of the room has to wait or go downstairs because the other occupant of the room is in the bathtub. A segragated wc would improve that ensuite. Remember to have a bench in the shower. The planning stage is an opportunity to plan for the future too, allowing space for a walker or wheelchair and space to install a lift. Think about which internal walls would benefit from sound insulation.

Note we have two steps down into our living room with ceiling at same level as rest of our house. There is no door on our living room so heat disappears up the stairs in winter leaving our feet cold.

So my recommendation is to ensure you have a door on hall to close off the back of house for heating. Particularly as your heat will also disappear up to your second floor.

great advice Kate...as you know separating spaces makes noise and heat control much easier and in an old house we found a ceiling height heavy curtain made a worthwhile improvement but much better to add a solid core door when building new

In my experience a door placed to control heat/cool/noise between the family and the rest of the house would need to be stepped back from the top of the steps allowing for a small landing for easy safe use