Looks good. Agree with bone re voids

It looks like the upper windows are full length awning windows with wind out fittings. That may get annoying having to bend down to ground level every time you wish to open or close the window. I’d also use carpet instead of laminate in WIR2, nicer underfoot and even though it abuts the ensuite, carpet is more forgiving of splashes than laminate.

In your laundry it looks like the cabinetry butts up to the glass sliding door. Consider changing the sliding door to a standard door so you can run the bench top right through to the wall.

I would look to change position of toilets in both powder rooms, ie not facing the door. plus make access to front powder room from passageway and not study area. There's a large waste of space to allow access to this powder room which could be used for linen storage etc And as OKL mentioned there's no provision for toilet bathroom for the pool, have you planned this within the Gym? Plus bigreaders comment on laundry to replace sliding door with single glass door is important. for better use of that space.

Agree. Pop a loo in the gym. If the guest bedroom is only for guests, I’d ditch the WIR, you’ll get the same hanging space with a BIR, then make the ensuite a dual ensuite and powder. This will allow a bigger study and free up the budget for a gym loo.

adding furniture helps explain some of my suggestions including reducing and/or rearranging the size of some of larger rooms in favour of increasing the size of some smaller rooms..eg a bigger guest ensuite with alternate doorways and more standing room in the wiw, moved the entry coat and display spaces, rearranged pwdr and enlarged study and laundry, added opt laundry chute from upstairs, minor alterations to kitchen and pantries, alt location for cellar and access to alfresco and outdoors plus a bathroom and mudroom entry for use from pool, alfresco, gym, garage, patio and outdoors ...upstairs has swopped small wiws for about double the storage with biw, all minor bedrooms are the same size with space for queen sized beds, the family bathroom and all storage is more spacious with an opt extra toilet in the bathroom plus the upstairs pwdr, the biw for bed 2 and bed 4 adds more privacy and sound control between bedrooms and master ens and there's an alternate shape for ens and master wiw providing more wall storage space for two sharing, there's a study nook and more spacious landing at the top of the stairs and the rumpus has space for a small pool, ping pong table or lounge and TV ... it's a very big house so you need to check furniture arrangements to make sure that the rooms are sized and arranged to suit your purpose eg my location of the TV in the media room allows for more comfortable placement of furniture for group viewing and rotating the pool to allow for a bigger outdoor patio but how will you use the small lounge or the rumpus and gym??

rethinking this very big house i found some ideas that save almost 90sqm and add some useful extras to consider

I would consider changing the front East facing windows for privacy from the street and ease of furniture placement